Thousands of Gaza residents broke into warehouses and distribution centres of the United Nations Palestinian refugee agency (UNRWA) grabbing flour and "basic survival items", the organisation said on Sunday.
"This is a worrying sign that civil order is starting to break down after three weeks of war and a tight siege on Gaza," the United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) said in a statement.
One of the warehouses, located in Deir al-Balah, is where UNRWA stores supplies from the humanitarian convoys crossing into Gaza from Egypt.
Aid supplies to Gaza have been choked since Israel began bombarding the densely-populated Palestinian enclave in response to a deadly attack by its ruling militant group Hamas on Oct. 7.
"Supplies on the market are running out while the humanitarian aid coming into the Gaza Strip on trucks from Egypt is insufficient," UNRWA said, adding that the current system to get humanitarian convoys into Gaza was "geared to fail".
"The needs of the communities are immense, if only for basic survival, while the aid we receive is meagre and inconsistent."
UNRWA has said that its ability to help people in Gaza has been completely stretched by air strikes that have killed more than 50 of its staff and restricted the movement of supplies.
Even before the conflict, the organisation had said its mandate was being jeopardised due to a lack of funding.
Established in 1949 following the first Arab-Israeli war, UNRWA provides public services including schools, primary healthcare and humanitarian aid in Gaza, the West Bank, Jordan, Syria and Lebanon.