UN Secretary General Ban Ki-moon says Israel only allows a meager amount of humanitarian aid to enter the impoverished Gaza Strip.
The United Nations strives to provide relief to one million people daily inside the coastal sliver which is home to 1.5 million people, Ban said during a news conference on Tuesday.
Israel, however, is only allowing supplies enough for 30,000 people to get through only one crossing, he added.
"We are experiencing serious difficulty in getting all the materials, humanitarian assistance, so it is absolutely necessary that they open the crossings," the secretary general said while announcing plans to launch a probe into Israel's bombing of UN compounds during its war on the Gaza population.
Ban told reporters that Israel has completely ignored his comments but said he "will continue to urge that" Tel Aviv allow more aid into the Palestinian strip.
Human rights watchdog Amnesty International has largely criticized Ban for being too timid on the extent of an inquiry into Israel's attack on its facilities.
"What is needed is a comprehensive international investigation that looks at all alleged violations of international law by all armed groups involved in the conflict," Irene Khan, the secretary general of Amnesty International, said in an announcement.
Khan added that researchers have found clear evidence of war crimes during the operation - in which more than 1300 Gazans have been killed and over 5300 others have been injured.