An Israeli air strike killed at least 10 people and wounded about 30 others on Sunday in a U.N.-run school in the southern Gaza Strip, witnesses and medics said, as dozens died in renewed Israeli shelling of the enclave.

The Israeli military declined immediate comment on the attack, the second to hit a school in less than a week.

A missile launched by an aircraft struck the entrance to the school in the town of Rafah, the witnesses and medics said. Hundreds of Palestinians in the area, where the Israeli military has been battling militants, had been sheltering in the facility.

Last Wednesday, at least 15 Palestinians who sought refuge in a U.N.-run school in Jabalya refugee camp were killed during fighting, and the U.N. said it appeared that Israeli artillery had hit the building. The Israeli military said gunmen had fired mortar bombs from near the school and it shot back in response.

Earlier on Sunday, Israeli shelling killed at least 30 people in Gaza, a day after Prime Minister Benjamin Netanyahu vowed to keep up pressure on Hamas even after the army completes its core mission of destroying a tunnel network that extends into Israel.