"At least six people were killed this afternoon when an UNRWA school was hit in Al-Maghazi refugee camp", in central Gaza, the UN agency said.

"The school was hit during Israeli forces air strikes and bombardment on the Gaza Strip," it said.

Dozens of people, including UNRWA staff, were wounded and the school suffered severe structural damage, it said, adding the number of casualties was expected to rise.

"At least 4,000 people have taken refuge in this UNRWA school turned shelter. They had and still have nowhere else to go," the agency said.

"This is outrageous, and it again shows a flagrant disregard for the lives of civilians," it added.

The Israeli military did not immediately comment on the incident when contacted by AFP.

Around 3,000 Gazans have been killed in Israeli strikes since the country's military started bombarding the Palestinian territory on October 7.

The conflict erupted when Hamas militants from Gaza launched attacks on multiple border communities and military posts in Israel.

More than 1,400 people have been killed in Israel during the war, while the army has identified 199 hostages abducted to Gaza.

United Nations Relief and Works Agency -- or UNRWA -- was established in 1949 to provide humanitarian assistance and protection to Palestinian refugees.

It operates in annexed east Jerusalem, the Gaza Strip, the occupied West Bank, Jordan, Lebanon and Syria.