GAZA (Reuters) - Israeli tank fire killed two boys at a U.N.-run school in the northern Gaza Strip Saturday, not six people as previously reported, a U.N. official said.

An Israeli army spokesman said he was checking the report.

Adnan Abu Hasna, a spokesman for the U.N. Relief and Works Agency (UNRWA), said two brothers had been killed and 14 people had been wounded, including the boys’ mother, when Israeli tank fire hit a school run by UNRWA in the northern town of Beit Lahiya.

Palestinian medics had earlier put the death toll at six.

“Israel must be held accountable for what happened,” Abu Hasna told Reuters.

About 45,000 Gazans fleeing battle zones are sheltering in U.N.-run schools in the enclave.

Hospital staff in Gaza said four Palestinians had died in other violence Saturday morning, including three killed by a tank shell that hit a residential area.

The military, which said it hit about 50 targets in the Gaza Strip overnight, said it was also checking that report.

More than 1,150 Palestinians have been killed and 5,100 wounded, many of them civilians, since Israel launched an air blitz on Gaza on December 27 and sent in ground forces a week later.

Ten Israeli soldiers and three civilians, hit by rockets fired from Gaza, have been killed during the campaign.