The 31-year-old blogger, who went by the handle "Minerva" after the Greek goddess of wisdom, rocketed to fame in South Korea for his startlingly accurate predictions about the economy, including the collapse of Lehman Brothers.

But prosecutors said he went too far in saying on an online discussion site that the government had banned major financial institutions and trade businesses from purchasing U.S. dollars in an apparent move to shore up the local currency, calling it inaccurate information that disrupted the foreign exchange market.

His arrest last week ignited a debate about freedom of speech in cyberspace in South Korea, one of the world's most wired and tech-savvy nations.

Prosecutors have extended the detention period for the blogger, identified in court documents as Park Dae-sung, for further questioning and plan to indict him next week, Yonhap news agency reported, citing an unidentified prosecution official.

Prosecutors were not immediately available for comment late Friday.

In some 100 postings on bulletin boards on a popular Internet portal last year, "Minerva" denounced the government's handling of the economy and made predictions, largely negative, for the future. His writings were sprinkled with jargon that suggested he was an economic expert, and his identity was a hot topic of discussion in South Korea.

Prosecutors say the suspect is actually an unemployed Seoul resident who studied economics on his own after graduating from a vocational high school and junior college with a major in information and communication.

Judge Hou Man of Seoul Central District Court ruled Thursday that the suspect must remain in custody, saying he was a risk for fleeing or destroying evidence, defense lawyer Park Chan-jong said.

The lawyer said the blogger did not intend to harm the public. If convicted of spreading false information, he faces up to five years in prison or a fine of up to 50 million won ($36,360).