UNITED NATIONS - A UN investigation on Tuesday accused Israel of spreading false statements about its attacks on United Nations schools and other facilities during the Gaza military campaign - including one reported to have killed more than 40 people - and formally demanded compensation.

The investigation ordered by Secretary General Ban Ki-moon found conclusively that Israeli weaponry - some containing white phosphorus - was "the indisputed cause" of attacks on several schools, a health clinic and the world body's Gaza headquarters.

Put on the defensive against widespread international criticism and accusations of possible war crimes in Gaza, Israel denies that it intentionally struck the compounds, and says it was forced to act against militants using the buildings and other civilian areas for cover. Israel said the material its government presented to the UN was largely ignored in the final report, which it called "biased."

Ban, whose release of the investigative report coincided with a monthly news conference, said he commissioned the investigation by a five-member board in January to look at the nine most serious incidents involving UN personnel and facilities. The Israeli military has said that several internal investigations into its conduct during the war in Gaza found that it acted according to international law.

The first of 11 recommendations calls for the UN to seek "formal acknowledgment by the government of Israel that its public statements alleging that Palestinians fired" from within the UN's school in Jabalia on Jan. 6 and within the UN's field office compound on Jan. 15 "were untrue and are regretted."

Another says the UN should "take appropriate action to seek accountability and pursue claims to secure reparation or reimbursement for all expenses incurred and payment made by the United Nations" because of deaths and injuries involving UN personnel and property.

In his presentation Tuesday, Ban took pains to point out, however, that Israeli citizens in southern Israel "faced and continue to face indiscriminate rocket attacks by Hamas and other militant groups."

He also mitigated the conclusions by attaching a letter at Israel's request emphasizing that the board he appointed to conduct the investigation "is not a judicial body or court of law: it does not make legal findings and does not consider questions of legal liability." The board was headed by Ian Martin of Britain, who recently stepped down as the UN envoy to Nepal.

Ban also commended Israel for its co-operation, and said there would be no inquiry beyond the UN-related casualties and damages in Gaza. He said the board's full report would remain confidential.

But Israel's deputy UN ambassador, Daniel Carmon, called the report "biased" and "one-sided."

Further, he said the commission was "betraying" Israel's confidence by going beyond the scope of what it was supposed to investigate.

"For us it was quite a shock to see the report. Not because we were surprised there was criticism - I mean, we were ready to receive criticism - but the scope and especially the issues that are tackled in this report," Carmon said.

In one strike near a UN school in Jabalia more than 40 people were killed, according to Gaza officials. At the time, witnesses told The Associated Press they saw a small group of militants firing mortar rounds from a street near the school.

An Israeli shell targeted the militants, but it missed and they fled, the witnesses said. Another three shells landed nearby, exploding among civilians, the witnesses said, refusing to allow their names to be published because they feared for their safety.

The UN investigation concluded that "the undisputed cause ... was the firing of 120 mm mortar rounds" by the Israel military "which landed in the road outside the school and at the compound of a family home nearby." It also said the army "had not maintained an adequate safety distance between whatever its target point may have been and the school."

Ban said the purpose of the investigation, which he described as "completely independent" from his staff, was to establish a record of what happened.

He also denied that the report was "watered down" in any way to please Israel's main supporter, the United States. "I do not have any authority to edit or change conclusions on this," he said.

Israel launched the offensive in Gaza on Dec. 27 to weaken Gaza's Hamas government and end years of rocket attacks by the Islamic militant group.

The three-week war killed some 1,400 Palestinians, most of them civilians, according to Gaza health officials and human rights groups. Israel says the number was lower and a majority of the dead were militants.

Thirteen Israelis were killed.

"The spirit of the report and its language are tendentious and entirely unbalanced and ignore the facts as they were presented to the commission," Israel's Foreign Ministry said in a statement. "The commission prefers the positions of Hamas, a murderous terror organization, and by doing so misleads the world public."