DHAKA: Israel launched a deadly attack on a UN school housing refugees in Gaza despite repeated warnings that civilians were sheltering there, the UN has said.

UN spokesman Chris Gunness said "the world stands disgraced" by the attack, in which 15 were reported killed.

The Israeli military said an initial inquiry suggested soldiers responded after militants had fired mortar shells "from the vicinity of the [UN] school".

Some 1,200 Palestinians and 55 Israelis have been killed in the conflict.

Most of the Palestinian deaths have been civilians.

Some 53 Israeli soldiers have been killed along with two civilians. A Thai worker in Israel has also died.

Israel launched its offensive in Gaza after a surge in rocket fire from the territory.

Hamas, which controls Gaza, says it will not stop fighting until the blockade, maintained by both Israel and Egypt, is lifted.

The current conflict is now the longest between Israel and militants from Gaza.

A 2012 offensive lasted for eight days, and the 2008 conflict went on for 22 days.

Mr Gunness from the UN Relief and Works Agency (UNRWA) told the BBC that Israel had been told 17 times that the school in the Jabaliya refugee camp was housing the displaced.

"The last time was hours before the fatal attack," he said.

"Our initial assessment is that it was Israeli artillery that hit our school."

Chris Gunness: "Children were killed as they slept next to their parents"

He said there were "multiple deaths" including women and children, adding that the attack caused "universal shame".

Images from the school showed large holes in the walls and roof.

Bob Turner, UNRWA's Gaza director, said the UN was "confident" Israel was responsible.

He said UN workers had collected fragments of projectiles that suggested they were artillery shells fired from Israeli positions to the north-east of the school.

The Israeli military said the incident was under review.

The military said in a statement that its "initial inquiry suggests that militants fired mortars earlier this morning from the vicinity of UNRWA school in Jebalia".

BDST: 1803 HRS, JUL 30, 2014