UNITED NATIONS (Reuters) - The U.N. Security Council should look into possible violations of international law during Israel’s three-week war in the Gaza Strip, a senior U.N. official said on Tuesday.

Karen AbuZayd, head of the U.N. relief agency in the Palestinian territories UNRWA, told the 15 council members that they shared part of the burden of helping the 1.5 million Palestinians in Gaza return to normalcy.

This, she said, includes supporting “moves to investigate apparent contraventions of international law, including direct attacks on U.N. personnel and facilities, as in UNRWA’s own headquarters and five of its schools.”

Britain’s Deputy U.N. Ambassador Karen Pierce told reporters before the meeting that London believed some of the allegations against both Israel and Hamas militants warranted further investigation, though not necessarily by the United Nations.

“I do think there are some credible allegations of the use of things like white phosphorus, which bear investigation,” she said, adding the initial probe should be undertaken by Israel.

White phosphorus munitions can cause extreme burns. The Israeli military has opened an investigation into white phosphorus use during the conflict.

“At the same time one has to remember that a non-state actor, namely Hamas, is also involved in some of these alleged breaches of international humanitarian law and one would want to find a way of ensuring that was properly looked into,” Pierce said.

She said the council would discuss the issue but would likely stop short of issuing a formal mandate for a Security Council investigation of any alleged war crimes. The council was not expected to reach any decisions about the conflict during Tuesday’s consultations.

New York-based Human Rights Watch called for an impartial international investigation of allegations that both Israel and Hamas were guilty of “serious violations of the laws of war.”

‘SYSTEMATIC DESTRUCTION’

Richard Falk, a special U.N. investigator sent to the Middle East by the Geneva-based U.N. Human Rights Council, has said there was evidence that Israel committed war crimes in the Gaza Strip and there should be an independent inquiry.

Falk, who is Jewish, has compared the situation in Gaza to that of the Warsaw Ghetto during the World War Two, where the Nazis systematically starved and murdered Jews. Israel denies committing any war crimes during its assault on Gaza.

Israel killed some 1,300 Palestinians, many of them civilians, and wounded 5,000 in the war. Palestinians killed 10 Israeli soldiers and three civilians, hit by cross-border rocket fire.

AbuZayd told the council she had seen in Gaza “what appears to have been systematic destruction to schools, universities, residential buildings, factories, shops and farms.”

U.N. humanitarian chief John Holmes said Hamas’ “reckless and cynical use of civilian installations” and “indiscriminate firing of rockets against civilian populations” in Israel were clear violations of international law.

He said there were “major questions to be asked” about the Israeli military’s failure to effectively protect civilians and humanitarian workers in Gaza.

Holmes also said that around 1.3 million Gazans -- roughly 90 percent of the strip’s population -- needed food aid. He added that the United Nations would launch a flash aid appeal next week to raise funds for emergency relief in Gaza.