GAZA CITY, Gaza — An Israeli bombardment hit outside a U.N. school where hundreds of Palestinians had sought refuge today, and Palestinian medics said at least 34 people died as international outrage grew over civilian deaths.

It was the second fatal strike in the vicinity of a U.N. school in hours, and the deadliest incident since Israel sent ground forces into Gaza last weekend. The ground operation is part of a larger offensive against the ruling Hamas militant group that has killed nearly 600 Palestinians, including dozens of civilians, according to U.N. and Palestinian officials.