"The defense minister said to me it was a grave mistake and he took it very seriously. He assured me that extra attention will be paid to UN facilities and staff and this will not be repeated," Ban added.

The United Nations Relief and Works Agency (UNRWA) said its compound, where up to 700 Palestinians were being sheltered, was hit twice by fire and three staff members were wounded.

Ban met Israeli Foreign Minister Tzipi Livni earlier Thursday as a part of a visit to the region aimed at bringing an end to the 10-day Israeli offensive on Gaza.

Last week Israeli forces shelled another UNRWA installation, the Fakhoura girls school in Jabaliya, killing more than 40 Palestinian civilians.