The United Nations headquarters in the Gaza Strip came under Israeli attack today.

The compound has been serving as a shelter for hundreds of people fleeing Israel's devastating offensive in Gaza. A UN spokesman said at least three people were wounded.

The compound includes the headquarters of the UN agency for Palestinian refugees, other offices and a school.

The attack came as UN chief Ban Ki-moon was in Israel trying to promote a cease-fire.

He expressed "strong protest and outrage" to Israel over the shelling and demanded an investigation.

He said Israeli Defence Minister Ehud Barak told him it was a "grave mistake".

The al-Quds hospital in the Tel al-Hawa neighbourhood is also reportedly on fire and a building housing several central media outlets, including the Reuters news agency, was also hit. Two journalists were said to be seriously wounded. Another press building was also struck.