Reuters says Israeli tank shells killed more than 40 Palestinians at a U.N. school in Gaza where civilians had taken shelter.

The report quoted witnesses as saying that two Israeli tanks shells exploded outside the school on Tuesday, killing at least 42 civilians and wounding dozens.

Medical officials said most of those who were killed were refugees from the northern parts of Gaza.

A senior UN official in Gaza said 350 people had been seeking shelter at the school when the shells hit and that the United Nations regularly gave the Israeli army exact geographical coordinates of its facilities to try to keep them safe from attack.