A United Nations fact-finding mission investigating the three-week war in Gaza last winter issued a highly critical report on Tuesday detailing what it called extensive evidence that both Israel and Palestinian militant groups took actions amounting to war crimes, and possibly crimes against humanity.

While the long-anticipated, 575-page report condemned rocket attacks by Palestinian armed groups against Israeli civilians, it reserved its harshest language for Israel’s treatment of the civilian Palestinian population in the Gaza Strip, both during the war and through the longer-term blockade of the territory.

The report called Israel’s military assault on Gaza “a deliberately disproportionate attack designed to punish, humiliate and terrorize a civilian population, radically diminish its local economic capacity both to work and to provide for itself, and to force upon it an ever increasing sense of dependency and vulnerability.”

The mission — led by Richard Goldstone, a respected South African judge and once the lead war crimes prosecutor for former Yugoslavia and Rwanda — did not attempt an exhaustive look at the war, instead focusing on 36 cases that it said constituted a representative sample. In 11 of these episodes, it said the Israeli military carried out direct attacks against civilians, including some in which civilians were shot “while they were trying to leave their homes to walk to a safer place, waving white flags.”

In all but one of these civilian attacks, the report said, “the facts indicate no justifiable military objective” for them.

The report cited other possible crimes by the Israelis, including “wantonly” destroying food production, water and sewerage facilities; striking areas, in an effort to kill a small number of combatants, where significant numbers of civilians were gathered; using Palestinians as human shields; and detaining men, women and children in sand pits. It also called Israel’s use of weapons like white phosphorus “systematically reckless,” and called for banning it in urban areas.

On the Palestinian side, the report said that firing rockets that either deliberately were aimed at Israeli civilians or were so inaccurate as to risk hitting civilians caused widespread trauma and constituted a war crime. It also singled out Palestinian actions within Gaza, including killings and other abuse of members of the rival Fatah political movement as a “serious violation of human rights.”

The four members of the fact-finding mission called on both the Israeli government and the Palestinian Authority to carry out serious, independent investigations. If that did not occur within the next six months, the mission said, the United Nations Security Council should refer the matter to the International Criminal Court.

The Israeli government said it was studying the report, but Gabriela Shalev, the Israeli ambassador to the United Nations, quickly rejected it, saying it failed to take into account that the operation was in “self-defense.”

In a statement, the Foreign Ministry said it had refused to co-operate with the mission, calling it biased from the start.

In Gaza, a spokesman for Hamas said it fired the rockets at Israel to try to defend itself. “We did not intentionally target civilians,” said Ahmed Yousef, a Hamas adviser. “We were targeting military bases, but the primitive weapons make mistakes.”

Palestinian armed groups have launched about 8,000 rockets and mortars into southern Israel since 2001. During the conflict, the report said, they killed 3 Israeli civilians and a soldier, and injured over 900 people.

But the report did not take a position on the number of Palestinian casualties, noting that they ranged from the Israeli government figure of 1,166 to the Hamas number of 1,444, without saying how many were civilians.

Israel had tried to discredit the mission from the start, saying that the United Nations Human Rights Council has a long record of bashing Israel. The report was released Tuesday to give members of the council time to study it before the panel formally presents it on Sept. 29, said Doune Porter, a spokeswoman for the fact-finding mission, calling it a standard procedure.

The United States recently joined the council. Ian Kelly, a State Department spokesman, said officials were reviewing the report.

Judge Goldstone said the panel heard extensive testimony, conducting 188 interviews and reviewing 10,000 pages of documents and 1,200 photographs. After Israel refused to allow the investigators into the country, the Human Rights Council paid for Israeli witnesses, including the mayor of Ashkelon and Israeli victims, to give testimony in Geneva.

The panel rejected the Israeli version of events surrounding several of the most contentious episodes of the war.

Israel’s mortar shelling near a United Nations-run school in the Jabaliya refugee camp, which was sheltering some 1,300 people, killed 35 and wounded up to 40 people, the report said.

The investigation did not exclude the possibility that Israeli forces were responding to fire from an armed Palestinian group, as Israel claimed, but said that this and similar attacks “cannot meet the test of what a reasonable commander would have determined to be an acceptable loss of civilian life for the military advantage sought.”

Israel repeatedly accused Hamas of using mosques to shelter armed men or munitions, and a report by Israel said an attack against the Maqadmah mosque in Jabaliya had killed six known militants.

But the Human Rights Council report said the attack came during evening prayers, when some 300 men and women were in the mosque, and killed 15 people. There were no secondary explosions to indicate the presence of an arms cache.

If Israel wanted to destroy a mosque suspected as an arms cache, it should have done so in the middle of the night, Mr. Goldstone said.

The report also noted that some 10 Israeli shells, including white phosphorus, hit the main Gaza City compound of the United Nations Relief and Works Agency while up to 700 civilians were sheltered there. The compound contained a huge fuel depot, but the shells kept coming, it said, though United Nations officials spoke to their Israeli military liaison repeatedly.

In another episode, the report said the destruction of a house in which nearly two dozen relatives died, appeared to be “the result of deliberate demolition and not of combat.”

Asked about accusations that he was anti-Israel, Judge Goldstone acknowledged he was Jewish and said, “It is grossly wrong to label a mission or to label a report critical of Israel as being anti-Israel.”

Isabel Kershner contributed reporting from Jerusalem, and Taghreed El-Khodary from Gaza.