"This is huge," says John Walsh, a senior associate at the Washington Office on Latin America, a human rights and democracy group. "It sets a precedent for the region."

This is the first time a former head of state has been extradited back to the country he once led to face justice.

Former Serbian president Slobodan Milosevic was handed over to an international court. But previous similar cases have been the result of executive branch negotiations. This marks the first time a national court has handed a leader over to a domestic court of another nation, say human rights experts. "This is a victory against the impunity that we have been accustomed to in Latin America. It is a major step forward for Chile, Peru, and the region as a whole," says Gloria Cano, a human rights lawyer in Lima.

A Peruvian court will now try Fujimori on charges ranging from his alleged approval of a death squad killing of 25 people to giving his intelligence chief, Vladimiro Montesinos, a $15 million "retirement" package after he was fired.

Fujimori has been a controversial figure in Peru since his upset victory in the 1990 presidential election. He vanquished hyperinflation and a leftist insurgency at the start of his 10-year rule (1990-2000), but at the end was hounded by charges of corruption and human rights abuses.

His government began to unravel after the 2000 presidential election. A secretly taped video was leaked showing Mr. Montesinos bribing an opposition congressman. Swiss authorities announced that they had discovered bank accounts traceable to Montesinos. Peruvian prosecutors estimate that more than $1 billion was stolen during the Fujimori years.

Montesinos has been in prison since 2001 on an array of convictions, including a 20-year sentence for drug trafficking.

As pressure built, Fujimori used his participation in the 2000 Asia-Pacific summit in Brunei to bail on his presidency. He stopped off in Japan, his parents' homeland, and resigned via fax. He stayed for five years. Fujimori secretly left Japan in October 2005, flying to Chile with the idea of then entering Peru.

Investigators here say that Fujimori miscalculated the reaction in Chile, thinking that he would be afforded the same treatment as another former president, Argentina's Carlos Menem, who had sought refuge in Chile. Chile rejected an Argentine extradition request in 2004.

But Mr. Menem was married at the time to a Chilean, the charges against him were purely economic, and Argentina officials only wanted to question him. In the case of Fujimori, the major charge involved human rights, which is a delicate issue in Chile, given the brutal dictatorship of former Chilean leader Augusto Pinochet, and it came with reams of supporting information.

Fujimori faces charges in the murder of 15 people in Barrios Altos, an inner-city Lima neighborhood, in 1991 and the killing of 10 people at the La Cantuta college the following year. Fujimori is accused of approving the actions of the paramilitary group, Colina Group, that did the killing. The inter-American court system has already found the Peruvian state culpable in both cases. Peruvian prosecutors would like Fujimori sentenced to 30 years for this case. The corruption charges carry sentences from two to eight years.

"I have waited many years for this day. We can finally imagine that there might be justice for our children," said Raida Condor, whose son, Armando Amaru, was killed in the university slayings.

Fujimori's extradition has immediate resonance in Bolivia, where the government is expected to request the extradition of former President Gonzalo Sánchez de Lozada, who has lived in the US since being ousted in October 2003.

Rogelio Mayta, a human rights lawyer in Bolivia, says the Fujimori case "is a significant example for Latin America and will serve as a reference point for us."

Mr. Sánchez de Lozada is accused of unleashing the military on protesters calling for his resignation. More than 60 people were killed. Bolivian authorities have publicly called on the US government to return Sánchez de Lozada, but they are only now filing the legal paperwork.

The other active extradition case in Latin America involves former Panamanian leader Manuel Noriega.

Most leaders of the world's governments will attend. U.S. Secretary of State Condoleeza Rice will represent American interests at the meeting. President Bush will meet with the leaders of the UN and other governments at a dinner tonight.

The United States is the largest emitter of greenhouse gases in the world. But the U.S. has declined to sign a U.N. climate document, the Kyoto Protocol, ratified by most of the world's leading nations in 1997. The protocol expires in 2012.

Those close to the scene are looking for a change in U.S. policy based on a series of reports released this year by a worldwide panel of scientists concluding that the scientific proof for climate change is "unequivocal."

"What the United States does, and how the United States decides to enter this negotiation is going to be a very, very telling commentary on the future of the climate negotiations, and ultimately, I believe, on the fate of the earth," said Tim Wirth, president of the U.N. Foundation and a former U.S. Senator from Colorado. Wirth represented the Clinton Administration during U.N. climate negotiations in 1995.

At a news conference last week sponsored by the National Environmental Trust, Sen. John Kerry (D-Mass.) was hopeful about the meeting.

"I'd like to see the President of the United States take the lead and say the United States of America is going to set fixed targets, that we're going to lead the world in alternative renewable fuels and technologies, and we're going to help contribute to the technical assistance and the technologies, themselves, to less developed countries in an effort to facilitate their economic transformation," Kerry said.

Iraqi government statements have been contradictory on the Sept. 16 gunfire, in which Blackwater USA, based in North Carolina, is accused of having killed Iraqi civilians while escorting an American diplomatic convoy in Baghdad. They range from threats to prosecute Blackwater to promises not to expel the firm from Iraq.

But the government of Prime Minister Nouri al-Maliki has managed to galvanize broad-based opposition to an order issued in the waning days of direct American rule in Iraq that lays out broad immunity from criminal prosecution for U.S. diplomats, troops and private contractors operating in Iraq.

It is known as Order 17, issued by the U.S. Coalition Provisional Authority in 2004. Iraqi officials have long chafed at the law, viewing it as an encroachment on Iraqi sovereignty. But until now, no serious effort has been made to revise it.

The central government, unpopular on the streets and worried about being marginalized, appears to be using the Blackwater crisis to counter U.S. criticism that it is ineffective and to show ordinary Iraqis that it can stand up to Washington.

The plane carrying the 69-year-old former ruler landed in a heavy mist at Lima's Las Palmas air force base, a day after Chile's Supreme Court authorized his extradition. He was then flown by helicopter to a police base, where he is to be held until a permanent facility is prepared for his detention.

Some 700 supporters who gathered outside the police air terminal across town to greet him were frustated when his plane was diverted to the air base.

"We have come to welcome Fujimori, to tell him that we are with him and will accompany him wherever he goes so that he feels he has the support of his people," his daughter Keiko Fujimori, who was elected to Congress in 2006, told The Associated Press.

Fujimori's extradition from Chile has provoked reactions ranging from elation to indignation.

Some Peruvians believe he should be tried for his controversial crackdown on the bloody Shining Path insurgency and alleged corruption during his 1990-2000 presidency.

But Fujimori maintains a following in Peru. A recent poll showed that 23 percent of Peruvians want to see him back in politics and some worry his return could provoke turmoil in a country emerging from decades of political and economic chaos.

"There will be a sector of the country that will identify with him, and he will play a destabilizing opposition role," said congressman Javier Valle Riestra, a leader of President Alan Garcia's Aprista party.

Fujimori was widely admired for ushering in economic stability and defeating the Shining Path rebel movement during his 1990-2000 government, but his presidency increasingly came under fire as it drifted toward authoritarianism and evidence surfaced of corruption.

He was flying to Peru under police custody Saturday, a day after the Chilean Supreme Court ordered his extradition on human rights and corruption charges.

Fujimori's followers and foes alike were stunned in November 2005, when he landed in a small plane in Chile and revealed his ambition to run for president in the 2006 elections, even though Peru's Congress had banned him from seeking public office until 2011. He was promptly arrested.

Fujimori had earned a reputation as a cool-headed strategist in handling multiple crises as president. But he may have miscalculated when he decided to leave his safe refuge in Japan, where he enjoyed immunity from extradition because of his Japanese nationality, inherited from his migrant parents.

One week after the gunbattle that killed 10 civilians and enraged Iraq's government, police and interior ministry officials were still gathering witness accounts and hunting video footage perhaps taken by amateurs on mobile phones.

Blackwater insists the US convoy it was escorting came under attack by insurgents before its guards opened fire but the Iraqi government was incensed by the incident and said it would revoke the security company's licence.

Traffic officer Ali Khalaf, who was on duty on Sunday last week in Al-Yarmukh, in the mainly Sunni Mansour area of west Baghdad, told AFP he had witnessed the entire incident.

"The American convoy arrived... and as usual I stopped the traffic to allow them to pass," Khalaf said.

As they often do, guards from the US firm -- the largest private security operators in Iraq -- hurled water bottles at cars to stop traffic as they drove through.

"Then without reason, they opened fire. Four shots, in the air, aiming just above the cars," Khalaf said.

"But one of the bullets struck a man in his car. I went to his aid but he was already dead, his body was slumped on the dashboard.

"His wife was then killed before my eyes by a bullet that hit her in the head."

Khalaf said he ran to take shelter inside his little hut as the gunfire continued.

The car with the dead couple "continued to move, with its doors open and the bodies inside -- like a phantom vehicle."

"The Americans fired at everything that moved, with a machine gun and even with a grenade launcher. There was panic. Everyone tried to flee. Vehicles tried to make U-turns to escape."

According to Khalaf, people then left their cars and tried to flee for cover, some being struck down as they ran. A car was hit by two grenades and burst into fire, engulfing its occupants in flames.

"There were dead bodies and wounded people everywhere, the road was full of blood. A bus was also hit and several of its occupants were wounded," said the traffic officer.

Two small black helicopters that always accompany Blackwater on security missions swooped down and sprayed the scene with machine gun fire, Khalaf added.

On Wednesday, the Iraqi and US governments announced they had set up a joint commission to investigate the shootings as well as to examine the broader question of rules governing foreign security companies operating in Iraq.

Despite opposition from Iraqi Prime Minister Nuri al-Maliki, Blackwater, which escorts US embassy personnel, was back on the streets of Baghdad on Friday after being grounded for four days.

According to a senior policeman involved in the investigations, other witnesses are equally adamant that Blackwater opened fire without provocation.

"The Americans say that the convoy first came under small arms fire. That is totally false," the officer told AFP, asking not to be named because he is not entitled to speak to the media.

"None of the witnesses we have interviewed speak of an attack," he said.

"There is at least one video, shot by police using a digital camera just moments after the shooting, which shows the victims," said the police officer. "This video is in our hands and we are examining it."

He did not rule out the possible existence of other videos taken at the moment of the shooting, including with mobile phones, given the number of people present at the time.

"The Blackwater guards opened fire on motorists without reason, they were never a target of a single shot or any attack," the officer said.

He said he was concerned that silence by world leaders "has been understood in Khartoum as a weakening of international resolve".

"It is time to break the silence," he said.