The UN Palestinian refugee agency (UNRWA) said thousands of Gaza residents had broken into its warehouses and distribution centers to take flour and "basic survival items."
"This is a worrying sign that civil order is starting to break down after three weeks of war and a tight siege on Gaza," Thomas White, UNRWA's director in Gaza, said in a statement.
Israel announced a near-total blockade and began carrying out airstrikes on the Gaza Strip following a deadly attack by militant Islamist group Hamas on October 7.
Since then, concern has been mounting about the deteriorating humanitarian situation in Gaza. The territory is ruled by Hamas, which is designated a terrorist organization by the US, EU, Germany and others.
UNRWA provides basic supplies to hundreds of thousands of people in Gaza. Its schools across the enclave are also being used as shelters for Palestinians displaced by the conflict.
UN chief says Gaza situation 'rapidly deteriorating'
United Nations Secretary-General Antonio Guterres has warned that the humanitarian situation in the Hamas-ruled Gaza Strip is declining rapidly.
The UN chief repeated his appeal for a cease-fire to end the "nightmare" of bloodshed.
"The situation in Gaza is growing more desperate by the hour. I regret that instead of a critically needed humanitarian pause, supported by the international community, Israel has intensified its military operations," Guterres said on a visit to the Nepalese capital, Kathmandu.
"The number of civilians who have been killed and injured is totally unacceptable."
Israel's military announced over the weekend it was entering "stage two" of the war with Hamas, stepping up its ground operation in Gaza. Israel has carried out airstrikes on the territory following an unprecedented attack staged by Hamas militants on October 7.
Humanitarian efforts to expand in Gaza: IDF
The Israel Defense Forces have warned they are moving towards their "next phase of war against Hamas," and asked civilians in Gaza to move to safer areas south of Wadi Gaza.
"Hamas terrorists operate inside and under civilian buildings, precisely because they know the IDF distinguishes between terrorists and civilians," Rear Admiral Daniel Hagari said in a video shared on social media platform X.
Hagari asked civilians in northern Gaza and Gaza City to move south of Wadi Gaza.
He also said humanitarian efforts led by Egypt and the US would be expanding in Gaza starting Sunday.
Israel has carried out airstrikes on Gaza and held the territory under a near-complete blockade since Hamas fighters carried out unprecedented terrorist attacks that killed 1,400 people in Israel on October 7.
According to the Health Ministry in Hamas-ruled Gaza, more than 7,700 Palestinians have been killed by Israel's bombardment.
Israel's military expanded its ground operation inside Gaza over the weekend. It also intensified airstrikes, knocking out internet and phone connectivity in the territory. Communications were gradually being restored on Sunday morning.
