Bombing Campaign

A senior Israeli military officer said Israeli troops shelled the UN headquarters in Gaza, wounding three UN staff, after coming under fire from Palestinian militants but a UN official has rebuffed that version.

UN official John Ging, who was in the compound at the time, called the Israeli account "nonsense."

At least two key medical facilities and two press buildings were also hit in separate incidents.

"It looks like phosphorus, it smells like phosphorus and it burns like phosphorus," said Chris Gunness, a spokesman for UNRWA, the aid agency for Palestinian refugees, about the situation at the compound.

Some 700 Palestinians were inside the building, seeking refuge from the fighting, when it was hit, but the UN has since evacuated them to a nearby elementary school.

Ban Ki-moon condemns attack

The attack drew sharp condemnation from international observers.

UN Secretary-General Ban Ki-moon, who was in Tel Aviv talking with Israeli officials about a ceasefire for the enclave, demanded an investigation, saying he had conveyed his "strong protest and outrage to the defense minister and the foreign minister."

He added: "Defense Minister Barak said to me it was a grave mistake."

EU Humanitarian Aid Commissioner Louis Michel told AFP news service he was "shocked and dismayed" at the shelling of the UN compound. He called for an independent investigation.

"It is unacceptable that the UN headquarters in Gaza has been struck by Israeli artillery fire," Michel said.

British Prime Minister Gordon Brown condemned the shelling as "indefensible" and "unacceptable."

"The intensification of Israeli military action, and continued Hamas rocket attacks, reinforce the urgency of our call for an immediate ceasefire," he said. "UN staff are working on behalf of the international community -- any attack on them is unacceptable, as Israel has acknowledged."

For its part, France also condemned the latest attack in the 20-day siege.

"We condemn in the strongest terms the bombings this morning by the Israeli army of several hospitals and a building housing international media in Gaza city," foreign ministry spokesman Eric Chevallier told AFP.

And Greece lodged a protest after Israel's navy turned back a boat chartered by Greek pro-Palestinian activists to take aid to the Gaza Strip, the foreign ministry reported.

The shelling set fire to the central warehouse in the UN compound, containing food and medicine, and fuel supplies were not safe from the fire, officials said. The compound houses large fuel reserves to allow humanitarian agencies to carry out their work.

Building was clearly marked

The UN was in the process of trying to move five fuel tankers out of the danger area.

"White phosphorus cannot be put out with water, but we do not have any sand in the compound," said Gunness.

The building was clearly marked with UN flags and officials were blaming Israel for the attack.

The UN has suspended all work in the area near the compound, but Gunness said that the agency was still working in other areas, bringing in humanitarian goods to the enclave.

Adnan Abu Hasna, also with UNRWA, denied there was any militant activity inside the compound.

A UN official said "there is no where safe to go" in Gaza City.

Hospital, journalists also hit

Also, the al-Quds hospital in the Tel al-Hawa neighborhood sustained serious damage in the early afternoon and one wing was on fire. A main building of the Palestinian Red Crescent was also hit.

A tower housing several central media outlets, including the Reuters news agency, was also hit, and two journalists were said to be seriously wounded. Another press building was also hit.

"These are buildings housing journalists working for international news agencies and must not be targeted," the Foreign Press Association (FPA) in Tel Aviv said, adding that it was "alarmed."

The buildings were known to the military to house press, the FPA said.

The Israeli military had no comment on the incidents.

Wake of destruction

At least seven Palestinian medics have been killed, three ambulances destroyed and other medical facilities, including a children's hospital, damaged since the Israeli military began its Operation Cast Lead on 27 December.

Several Palestinian journalists have also been killed and injured in the fighting. The Israeli military has banned foreign journalists from entering the Gaza Strip since the fighting began.

Last week, the Israeli military held talks with the UN during which it committed its troops to preserving the neutrality of the UN and the safety of the staff.