DEIR AL BALAH, Gaza (AP) — Israeli strikes killed more than a dozen people in the Gaza Strip early Friday, as Israel sent more ground troops into the Palestinian territory to ramp up its offensive against Hamas.

Authorities in Hamas-ruled Gaza accuse Israeli forces of a "heinous massacre" with a strike on a school they say killed almost 30 people, many of them children.

In pressing forward with its assault on the territory, Israel hopes to squeeze Hamas into releasing the remaining hostages. But other objectives have emerged.

The Israeli military will expand its ground operation in Gaza to occupy 25% of the enclave over the next two to three weeks, a senior Israeli official said in a briefing with reporters on Monday. Why it matters: The Israeli official said the ground operation is part of a "maximum pressure" campaign aimed at forcing Hamas to agree to release more hostages.

More than 1,000 people have been killed in Gaza since Israel resumed military operations last month, Palestinians say Israeli Prime Minister Benjamin Netanyahu said Wednesday that the military was "dissecting" the Gaza Strip and seizing territory to pressure Hamas into freeing hostages still held in the enclave.