WASHINGTON, May 6 (Reuters) - Nigerian medical experts concluded Pfizer Inc. violated international law during a 1996 epidemic by testing an unapproved drug on children with brain infections, the Washington Post reported in Sunday editions, citing a copy of the panel's confidential report.

The report, completed five years ago but never released, found that Pfizer (Research) was never authorized by the Nigerian government to give the unproven drug Trovan to nearly 100 children and infants at a field hospital in Kano, where they were being treated for an often deadly strain of meningitis.

Pfizer's experiment was "an illegal trial of an unregistered drug," and violated Nigerian law, the international Declaration of Helsinki that governs ethical medical research and the U.N. Convention on the Rights of the Child, the panel concluded, according to the Post.

Five children died after being treated with the experimental antibiotic and others contracted arthritis, although there is no evidence the drug played a part. Six children died while taking a comparison drug, the Post said.

At the time, Doctors Without Borders was dispensing approved antibiotics at hospital, according to the Post.

Pfizer, the world's biggest drug company, told the Post it conducted the trial with the full knowledge of the Nigerian government and consistent with Nigerian law. Local nurses explained the experiment to Nigerian parents and obtained their "verbal" consent, the company told the Post.

"Trovan unquestionably saved lives, and Pfizer strongly disagrees with any suggestion that the company conducted its study in an unethical manner," the Post quoted it as saying.

A U.S. federal judge last November dismissed a lawsuit that accused Pfizer of not properly warning Nigerian families about the risk of its meningitis drug Trovan, then awaiting U.S. Food and Drug Administration approval, during a clinical test. He said the case should be heard in a Nigerian court.

The lawsuit argued that some of the children in the trial died and others suffered brain damage because the drug makers did not explain to the Nigerian families that the antibiotic was experimental, that they could refuse the treatment for their children, or that other medicines were available.

Pfizer has denied the accusations.

The Nigerian government report obtained by the Post said there were no records indicating that Pfizer told the children or their parents that they were part of an experiment.

An approval letter from a Nigerian ethics committee, which Pfizer used to justify its actions, was a falsified document that had been concocted and backdated by the company's lead researcher in Kano, the Post said, citing the report.

The panel recommended that Pfizer be "sanctioned appropriately," that it issue "an unreserved apology to the government and people of Nigeria," and pay an unspecified amount of restitution, according to the Post.

It urged Nigeria to enact reforms to prevent a recurrence.

The FDA cleared Trovan for adult use in 1997, although it never approved the drug for use by American children.

Trovan was later associated with reports of liver damage and deaths, leading the FDA to severely restrict its use in 1999. European regulators banned the drug.

Rep. Tom Lantos of California, the senior Democrat on the International Relations Committee, described the report's findings as "absolutely appalling," and said he would introduce a bill requiring U.S. researchers to give regulators details of tests they plan in developing countries.