Six of the court's 11 justices upheld a 2005 law allowing embryonic stem cell research and turned down a petition filed that same year by then-Attorney General Claudio Fontelles, who argued the law was unconstitutional because it violates the right to life.

The remaining five judges argued that while the 2005 law is constitutional, research should only be carried out "with restrictions" such as not allowing the embryo to be destroyed and submitting each case for the approval of an ethics commission.

The ruling drew immediate fire from church officials in the world's largest Roman Catholic country.

The National Conference of Brazilian Bishops issued a statement saying it "regretted" the ruling, comparing it to a death sentence. The bishops' conference said its position "is not a matter of religion, but of the defense of human life, beginning with conception."

The law opens the way for research with embryos resulting from in-vitro fertilization that have been frozen for at least three years.

Advocates have said that a favorable Supreme Court ruling could make Brazil Latin America's leader in stem cell research.

They praise Brazilian scientists for their work with adult stem cells for the treatment of cardiovascular diseases and Type 1 diabetes, and have said that similar breakthroughs could be achieved with embryonic stem cells.