GAZA CITY, Gaza Strip — The United Nations' humanitarian chief suggested Thursday that Israel should pay for the hundreds of tonnes of food and other supplies destroyed when Israeli shells struck the main UN compound in Gaza.

Touring Gaza to assess what is most urgently needed in the coastal strip, John Holmes called the steep Palestinian casualty toll from Israel's offensive "extremely shocking" and suggested the UN might ask Israel to compensate it for wartime damage to UN compounds in Gaza.

Hundreds of tonnes of humanitarian aid were destroyed by Israeli shelling that struck the main UN compound.

"We want to make sure it is properly investigated and that we get proper accountability for it and proper compensation if it is needed and I think it will be needed," Holmes told reporters.

Israel waged a three-week war meant to end rocket fire on southern Israel from Hamas-ruled Gaza.

Nearly 1,300 Palestinians, a majority of them civilians, have died in the offensive, according to Gaza health officials. Thirteen Israelis were also killed, according to the government.

Israeli Prime Minister Ehud Olmert said the war could help hasten the return of a captive soldier long held by Palestinians in Gaza. Israeli media said some cabinet ministers have softened their positions on releasing Palestinian political prisoners in exchange for the soldier, signalling the government is trying to work out a deal with Hamas ahead of Israeli elections next month.

Violence on both sides has marred the ceasefire and on Thursday a Palestinian man and girl walking near the shore in Gaza City were wounded by a shell fired from an Israeli gunboat, a Gaza health official said.

Another shell landed 100 metres away in an empty area near a UN aid distribution centre. And heavy-calibre bullet fire struck at least one house in the area, a witness said.

The Israeli military said it was firing to deter a Palestinian fishing vessel that had strayed off-limits.

On the first day of a five-day trip to the region, Holmes said he was looking at immediate humanitarian needs and thinking about longer-term reconstruction in Gaza. The biggest concerns, he said, are providing clean water, sanitation, electricity and shelter to people displaced by the fighting.

Gaza's blockaded border crossings will have to be opened to allow reconstruction to begin, he said.

"Goods have to be able to get in freely and in the right quantities, including construction materials, so that reconstruction can start."