A U.N. report on Israel's military attack on a Palestinian refugee camp does not back up claims of a massacre, but it does criticize both sides for putting civilians in harm's way, Western diplomats said Wednesday.

The report accuses Israel of delaying aid and medical help to Palestinians in the Jenin refugee camp. And it charges Palestinian militants with deliberately putting its fighters and equipment in civilian areas in violation of international law, according to the diplomats.

The violence in Jenin came during an Israeli offensive launched on March 29 in response to a homicide bombing that killed 29 Israelis. The heaviest fighting during the period was in the Jenin camp, where the Palestinians said Israeli attacks killed 500 people.

On April 19, Israel approved a U.N. fact-finding mission to probe its military assault on Jenin but later objected to the team's makeup and mandate. The team was disbanded and the U.N. General Assembly then asked Secretary-General Kofi Annan to compile a report on what happened in the camp.

The report was also to look into attacks on other Palestinian cities assaulted by the Israeli army in what Israel called a campaign to destroy terrorist networks.

The long-awaited report, scheduled to be released on Thursday, said that between March 1 and the beginning of May, 497 Palestinians were killed during Israel's Operation Defensive Shield in the West Bank, according to diplomats who got advance copies and spoke on condition of anonymity.

That figure was almost double the death toll of 262 reported by the Red Crescent Society in the Palestinian territories for the same period.

But it said that in Jenin, 52 Palestinian deaths had been confirmed by April 18, and that up to half may have been civilians. It called the Palestinian allegation that some 500 were killed "a figure that has not been substantiated in the light of evidence that has emerged," the diplomats said.

Israel maintained that it fought fierce battles against Palestinian terrorists in which 52 Palestinians were killed -- the vast majority gunmen -- along with 23 Israeli soldiers. Human rights groups have said 22 civilians were killed in Jenin.

The U.N. findings mirrored those of Human Rights Watch, which said its experts had found nothing to back allegations of an Israeli army massacre.

The report was based on information from U.N. officials, the Palestinians, five U.N. member states, private relief organizations and documents in the public domain, the diplomats said. Annan wrote to the Israeli government asking for help in preparing the report but U.N. officials said Israel did not make a submission or respond to the letter.

Israel and the Palestinians received copies of the report late Wednesday but refused to comment until its release.

Israel has maintained that its army took all measures possible not to hurt civilians.

The report stresses the difficulty of authenticating information, noting that first hand accounts are partial and often anonymous, the diplomats said.

In criticizing the Palestinians, the report noted that much of the fighting took place in heavily populated civilian areas partly because the Palestinians put their fighters in those areas in breach of international law, the diplomats said.

It also criticized Israeli tactics that put civilians at risk, saying Palestinian civilians suffered because Israel delayed access to medical care and humanitarian aid. Curfews and closures imposed by Israel also contributed to civilian suffering, diplomats quoted the report as saying.