GAZA CITY, Gaza Strip » Israeli aircraft struck crowded areas in the Gaza Strip and killed a senior militant with a missile strike on a media center today, driving up the Palestinian death toll to 100, as Israel broadened its targets in the 6-day-old offensive meant to quell Hamas rocket fire on Israel.

Escalating its bombing campaign over the weekend, Israel began attacking homes of activists in Hamas, 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.

While Israel and Hamas were far apart in their demands, both sides said they were open to a diplomatic solution — and prepared for further escalation if that failed.

The leader of Hamas took a tough stance, rejecting Israel’s demands that the militant group stop its rocket fire. Instead, Khaled Mashaal said, Israel must meet Hamas’ demands for a lifting of 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."

An Israeli official said Israel hoped to find a diplomatic solution to the crisis as well and signaled Egypt was likely to play a key role in enforcing any truce.

"We prefer the diplomatic solution if it’s possible. If we see it’s not going to bear fruit, we can escalate," he said, speaking on condition of anonymity because of the sensitive diplomatic efforts under way.

The official said Israel doesn’t want a "quick fix" that will result in renewed fighting months down the road. Instead, Israel wants "international guarantees" that Hamas will not rearm or use Egypt’s neighboring Sinai peninsula for militant activity.

Overall, the offensive that began Wednesday killed 100 Palestinians, including 53 civilians, and wounded some 840 people, including 225 children, Gaza heath official Ashraf al-Kidra said.

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

Hamas fighters have fired more than 1,000 rockets into Israel in the current round of fighting, including 95 today, among them one that hit an empty school in the coastal city of Ashkelon. Israeli police spokesman Micky Rosenfeld said 29 rockets were intercepted by the Iron Dome anti-missile battery. Rockets landed in open areas of Beersheva, Ashdod, Ashkelon, and caused damage in a number of areas.

Schools in southern Israel have been closed since the start of the offensive on Wednesday, and large police units deployed in the area to respond to any potential damage and injuries from rockets.

A poll published in the Haaretz daily today showed widespread support in Israel for the offensive. It said that 84 percent of the public supports the operation, with 12 percent opposed. At the same time, it said just 30 percent of the public supports a ground invasion of Gaza. The poll, conducted by the Dialog agency, surveyed 520 people and had a margin of error of 4.4 percentage points.

In today’s violence, an Israeli airstrike on a high-rise building in Gaza City killed Ramez Harb, a senior figure in Islamic Jihad’s military wing, the Al Quds Brigades, 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.

Thick black smoke rose from the building. Paramedics said several people were wounded.

Islamic Jihad, a smaller sister group to Hamas, said it believed Harb was the target of the strike.

Israel has killed dozens of wanted militants in surgical strikes throughout the operation, the result, officials say, of intelligence gathered from its collection of high-flying drones overhead and a network of informants.

Before dawn today, 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.

The strike killed three adults and a 2-year-old boy, and wounded 42 people, al-Kidra said.

Residents said Israel first sent a warning strike around 2 a.m., prompting many to flee their homes. A few minutes later, heavy bombardment followed.

Ahed Kitati, 38, had rushed out after the warning missile to try to hustle people to safety. But he was fatally struck by a falling cinderblock, leaving behind a pregnant wife, five young daughters and a son, the residents said.

Sitting in mourning with her mother and siblings hours after her father’s death, 11-year-old Aya Kitati clutched a black jacket, saying she was freezing, though the weather was mild. "We were sleeping, and then we heard the sound of the bombs," she said, then broke down sobbing.

Ahed’s brother, Jawad Kitati, said he plucked the lifeless body of a 2-year-old relative from the street and carried him to an ambulance. Blood stains smeared his jacket sleeve.

Another clan member, Haitham Abu Zour, 24, woke up to the sound of the warning strike and hid in a stairwell. He emerged to find his wife dead and his two infant children buried under the debris, but safe.

In another area of Gaza City, the patriarch of the Daloo family, Jamal, sat in mourning for 11 members of his family killed in a missile strike on his home Sunday. Among the dead were his wife, his son, daughter-in-law, his sister and four grandchildren. He embraced relatives and neighbors paying their condolences, his face swollen from crying. He disputed Israel’s initial claim that a senior Islamic Jihad operative was hiding in his house.

The mourners sat in plastic chairs just meters away from bulldozers clearing the ruins of Daloo’s home. His 16-year-old daughter Yara was still missing and believed under the rubble, family members said.

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.

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.

U.N. Security General Ban Ki-moon also arrived in Cairo to appeal for an end to violence.

The rising toll was likely to intensify pressure on Israel to end the fighting. Hundreds of civilian casualties in an Israeli offensive in Gaza four years ago led to fierce international condemnation of Israel.

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.

Israel has been jittery that a second front along its northern border could be opened, either by militants in Lebanon or from spillover from the Syrian civil war.

Lebanese military experts dismantled two Katyusha rockets today that were equipped with timers and ready to fire at Israel, a senior Lebanese security official said, speaking on condition of anonymity in line with military regulations.

Associated Press writers Hamza Hendawi and Maggie Michael in Cairo and Zeina Karam in Beirut contributed to this report.