Intense bombardment of a Gaza Strip city filled with refugees flattened a large mosque and killed or wounded scores of people on Thursday as Israel repeated its intention to push into the area with ground forces if Hamas does not release hostages before the start of the Muslim holy month of Ramadan.

Nearly 100 people were killed across the enclave from Israeli strikes over the past day, health authorities in Gaza said Thursday, bringing the total death toll after almost 20 weeks of war to nearly 30,000.

Around half of the Gaza Strip’s population of 2.3 million people are crammed into the southern city of Rafah along the border with Egypt, where the strike on the mosque occurred Thursday. Wafa, the Palestinian news agency, reported that at least seven Palestinians had been killed overnight in Rafah and dozens more wounded.