GAZA CITY, Gaza Strip — Israel stepped up its campaign against Gaza’s ruling Hamas on Thursday, killing three of the group’s senior military commanders in an airstrike that pulverized a four-story home, the second such attack targeting top leaders in two days.

The pinpoint pre-dawn attack on Hamas’ inner sanctum was launched minutes after the men emerged from tunnel hideouts, a security official said – displaying the long reach of Israel’s intelligence services.

The killing of the commanders, who played a key role in expanding Hamas’ military capabilities in recent years, was bound to lower morale in the secretive group, but might not necessarily diminish its ability to fire rockets at Israel.

Thursday’s strike in the southern Gaza town of Rafah, coupled with a Cabinet decision to call up 10,000 more reserve soldiers, signaled an escalation in the Israel-Hamas war after Egyptian cease-fire efforts collapsed this week.

Since July 8, fighting has claimed more than 2,000 Palestinian lives, most of them civilians, according to Palestinian officials and the U.N., and entire neighborhoods of Gaza have been destroyed. Sixty-four Israeli soldiers, two Israeli civilians and a guest worker also have been killed.

The resumption of Gaza fighting came after several failed rounds of indirect talks of Israel and Hamas in Cairo. Since the breakdown of the talks violence has continued at a steady pace.

On Thursday, more than 100 rockets were fired from Gaza, while Israel carried out some 50 airstrikes, the Israeli military said.

In all, at least 25 Palestinians were killed or their bodies recovered Thursday, among them five children, bringing the total since July 8 to 2,074, according to Gaza health official Ashraf al-Kidra. More than 10,200 people have been wounded and some 100,000 left homeless.

An Israeli man was also seriously hurt Thursday, when a mortar shell fired from Gaza exploded outside a kindergarten in southern Israel and shrapnel flew through a window as he celebrated his son’s third birthday.

In Gaza, one of those pulled from the rubble Thursday was Sara Deif, the 5-year-old daughter of Mohammed Deif, the top Hamas military leader who was apparently the target of an airstrike on a three-story home in Gaza City late Tuesday.

Deif’s wife and infant son were also killed in the attack. Hamas said Deif, who has survived four previous attempts on his life, some with serious injuries, was not in the area at the time of the strike. Israel has declined comment on Deif’s possible fate.

After Thursday’s airstrike in Rafah, the Hamas military wing, the Izzedine al-Qassam Brigades, announced that three senior commanders, Mohammed Abu Shamaleh, Raed Attar and Mohammed Barhoum had been killed.

Several hours later, thousands marched through Rafah in a funeral procession, firing guns, waving flags of different militant groups and chanting religious slogans. Those killed were carried aloft through the crowd on stretchers, wrapped in green Hamas flags.

Sami Abu Zuhri, a Hamas spokesman, said Israel “will not succeed in breaking the will of our people or weaken the resistance,” and that Israel “will pay the price.”

Israeli Prime Minister Benjamin Netanyahu praised the Shin Bet security service and its “superior intelligence” for the strike. The killing of the Hamas leaders was bound to buy him some time as Israel’s public grows impatient with the government’s inability to halt rocket fire from Gaza.

Israeli media said Netanyahu and Defense Minister Moshe Yaalon authorized the strike on the Hamas commanders in the four-story building in the Tel Sultan neighborhood of Rafah. A security official, speaking on condition of anonymity because he was not authorized to speak to reporters, said the trio had entered the home just minutes earlier, emerging from underground hideouts.

“We will continue to pursue and strike the heads of Hamas at any time and any place they may be. Whoever tries to harm Israel’s citizens – they are marked for death,” Yaalon said.

Israel’s military and the Shin Bet emphasized the importance of the three Hamas commanders.

Abu Shamaleh, 41, had been the top Hamas commander in southern Gaza, while Attar, 40, was in charge of weapons smuggling and the construction of attack tunnels, and had played a role in the capture of Israeli soldier Gilad Schalit in 2006. Barhoum, 45, was a senior Hamas operative in Rafah, a joint statement said.

In pinpointing the whereabouts of the Hamas commanders, Israel likely relied to some extent on local informers. Israel has maintained a network of informers despite its withdrawal from Gaza in 2005, at times using blackmail or the lure of exit permits to win cooperation.

Al Majd, a website linked to the Hamas security services, said Thursday that seven suspected informers were arrested in recent days and that three were killed “after the completion of the revolutionary procedures against them.”

It was the second time during the Gaza war that the website announced suspected informers had been killed by Hamas.

Deitch reported from Jerusalem. Associated Press writers Josef Federman and Yousur Alhlou in Jerusalem and Alexandra Olson at the United Nations contributed to this report.