Escalating its bombing campaign over the weekend, Israel began attacking homes of Hamas activists, the Islamic militant group that rules Gaza. These attacks have led to a sharp spike in civilian casualties, killing 24 civilians in just under two days and doubling the number of civilians killed in the conflict, a Gaza health official said.

The rising toll came as Egyptian-led efforts to mediate a cease-fire between Israel and Hamas got into gear. With the two sides far apart, the leader of Hamas took a tough stance, rejecting Israel’s demands that the militant group stop its rocket fire. Instead, he said, Israel must meet Hamas’ demands for lifting the blockade of Gaza.

“We don’t accept Israeli conditions because it is the aggressor,” he told reporters in Egypt. “We want a cease-fire along with meeting our demands.”

Hamas fighters have fired hundreds of rockets into Israel in the current round of fighting, including 75 on Monday. One hit an empty school. Twenty rockets were intercepted by the Iron Dome anti-missile battery, police spokesman Micky Rosenfeld said. Rockets landed in open areas of Beersheva, Ashdod, Asheklon. Schools in southern Israel have been closed since the start of the offensive Wednesday.

Overall, the offensive that began Wednesday killed 96 Palestinians, including 50 civilians, and wounded some 720 people, Gaza heath official Ashraf al-Kidra said. Among the wounded were 225 children, he said.

On the Israeli side, three civilians have died from Palestinian rocket fire and dozens have been wounded. An Israeli rocket-defense system has intercepted hundreds of rockets bound for populated areas.

In Monday’s violence, an Israeli airstrike on a high-rise building in Gaza City killed a leading militant in Islamic Jihad, the group said in a text message to reporters. A number of foreign and local news organizations have offices in the building, which was also struck on Sunday. A passer-by was also killed, medics said.

Islamic Jihad, a smaller sister group to Hamas, identified the dead militant as Ramez Harb, a senior figure in its military wing, the Al Quds Brigades. Thick black smoke rose from the building. Paramedics said several people were wounded.

Before dawn Monday, a missile struck a three-story home in the Gaza City’s Zeitoun area, flattening the building and badly damaging several nearby homes. Shell-shocked residents searching for belongings climbed over debris of twisted metal and cement blocks in the street.

Egypt is trying to broker a cease-fire with the help of Turkey and Qatar. Turkish Foreign Minister Ahmet Davutoglu and a delegation of Arab foreign ministers were expected in Gaza on Tuesday.

However, Israel and Hamas appeared far apart in their demands, and a quick end to the fighting seemed unlikely.

A senior Egyptian official told The Associated Press that Hamas and Israel were each presenting Egypt with their conditions for a cease-fire.

“I hope that by the end of the day we will receive a final signal of what can be achieved,” said the official, who is familiar with the indirect negotiations. He said Israel and Hamas are both looking for guarantees to ensure a long-term stop to hostilities. The official says Egypt’s aim is to stop the fighting and “find a direct way to lift the siege of Gaza.”

The official spoke on condition of anonymity because of the sensitivity of the indirect negotiations.

But Mashaal said Gazans were prepared to keep fighting.

Gaza’s demand is not a halt to war. Its demand is for its legitimate rights,” including a stop to Israeli attacks, assassinations and a lifting of the blockade, Mashaal said.

“Let those who started this crazy war stop it, on our conditions,” he said.