Secretary-General Ban Ki-moon ordered an investigation Tuesday into attacks on U.N. facilities in Gaza but Amnesty International protested that the inquiry should be much broader and include all alleged violations of international law by Israel, Hamas and other Palestinian armed groups.

Ban announced that he had initiated steps to establish a U.N. Board of Inquiry "into incidents involving death and damage at U.N. premises in Gaza." The board will be headed by Ian Martin of Britain, who recently stepped down as the U.N. envoy to Nepal, and will include legal advisers and a military expert, he said.

The secretary-general said the board should start work immediately and report to him within a month.

John Ging, who heads operations in Gaza for the United Nations Relief and Works Agency which helps Palestinian refugees, told reporters in a videoconference on Monday that over 50 U.N. installations were damaged during the Israeli air and ground attack that began on Dec. 27.

Ban has expressed anger at the "outrageous attacks against U.N. facilities" in Gaza, including several schools and the UNRWA compound in Gaza City. He said last month that he expects "a full explanation of each incident" from Israel, and that those responsible be held accountable.

The secretary-general said he informed both the Israeli government and the Palestinian Authority about the inquiry.

"I do not have any doubt that they will cooperate fully," he said.

Amnesty International Secretary-General Irene Kahn called Ban's announcement Tuesday welcome but insufficient.

"It is not only the victims of attacks on the U.N. who have a right to know why their rights were violated and who was responsible, and to obtain justice and reparation," she said in a statement. "What is needed is a comprehensive international investigation that looks at all alleged violations of international law — by Israel, by Hamas and by other Palestinian armed groups involved in the conflict."

Khan urged the secretary-general to immediately broaden the scope of the investigation, and she called on the Security Council to support a comprehensive inquiry "that covers all attacks that may have violated the laws of war during the recent fighting in Gaza and southern Israel."

Click to view photos from the conflict.