GAZA CITY, Gaza Strip — An Israeli airstrike in Gaza killed three senior commanders of the Hamas military wing Thursday, delivering a likely blow to the organization’s morale and highlighting the long reach of Israel’s intelligence services.

The pre-dawn strike leveled a four-story house in a densely populated neighborhood of the southern town of Rafah, killing six people, including the three senior Hamas commanders.

The trio had played a key role in expanding Hamas’ military capabilities in recent years, including digging attack tunnels leading to Israel, training of fighters and smuggling of weapons to Gaza, Israel said.

It was not immediately clear if their assassination would prompt a change in Hamas strategy in the current round of fighting with Israel or diminish the group’s ability to fire rockets at Israel. The military wing, the Izzedine al-Qassam Brigades, is a secretive organization.

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 “superior intelligence” of the Shin Bet security service and the military’s “precise execution” of the attack.

The killing of the three top Hamas commanders will likely buy Netanyahu some time as the Israeli public becomes increasingly impatient with the government’s inability to halt rocket fire from Gaza.

Israel and Hamas identified the three commanders killed in the 3 a.m. airstrike in Rafah’s Tel Sultan neighborhood as Mohammed Abu Shamaleh, Raed Attar and Mohammed Barhoum.

Gaza police and witnesses said several missiles hit the four-story building.

Hamza Khalifa, an area resident said the house was struck without warning. “We only heard multiple F-16 (warplane) missiles, one after the other, six or seven missiles,” he said.

Several hours later, a large earth mover was still clearing mounds of debris and wreckage.

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, in some cases 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.” The wording suggested they did not receive a trial.

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

The Rafah attack came a day after an apparent Israeli attempt to kill the top Hamas military leader, Mohammed Deif, in an airstrike on a house in Gaza City.

Deif’s wife and an infant son were killed in that strike, but the Hamas military wing said Deif was not in the targeted home at the time.

The back-to-back targeting of top Hamas military leaders came after indirect Israel-Hamas negotiations in Cairo on a sustainable truce broke down Tuesday. Gaza militants resumed rocket fire on Israel, even before the formal end of a six-day truce at midnight that day.

Since then, Hamas and other groups have fired dozens more rockets, and Israeli aircraft have struck dozens of targets in Gaza, dimming prospects for a resumption of the Cairo talks.

Despite the crisis, Palestinian President Mahmoud Abbas was holding talks in Qatar on Thursday with Hamas’ top political leader in exile, Khaled Mashaal, and the emir of Qatar. Before the collapse of the truce talks, Abbas had planned to use the meetings in Qatar to urge Mashaal and his Qatari backers to support an Egyptian cease-fire plan.

Hamas has rejected the Egyptian proposal, saying it contained no commitments by Israel to ease the border blockade of Gaza. The blockade was imposed by Israel and Egypt after the Hamas takeover of Gaza in 2007.

Hamas leaders said they could not accept a deal they feared would restore the closure regime that was in place before the start of the latest round of fighting on July 8. The border restrictions prevent most Gazans from traveling outside the crowded coastal strip and bar most exports.

Since the Gaza war erupted six weeks ago, more than 2,000 Palestinians have been killed and about 100,000 left homeless, according to the U.N. and Palestinian officials. Israel lost 67 people, all but three of them soldiers.

It was unclear if the killing of the three Hamas commanders would affect its ability to fire rockets. Israel estimated that Hamas had 10,000 rockets before the war and lost about two-thirds of its arsenal since then.

In a joint statement, the Israeli military and Shin Bet security service emphasized the importance of Abu Shamaleh, Attar and Barhoum to the Hamas military operation.

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

Abu Shamaleh was a confederate of Deif’s who was involved in planning and carrying out at least four major attacks on Israeli soldiers since the 1990s, including one in 2004 that killed four and wounded 10, the statement said.

Attar, it said, was responsible for orchestrating a series of complex attacks on Israeli targets, including through the Sinai Peninsula in neighboring Egypt.

“This morning’s strike sends a clear message to those responsible for planning attacks, we will strike those that have terrorized our communities, towns and cities, we will pursue the perpetrators of abduction of our soldiers and teenagers, and we will succeed in restoring security to the State of Israel,” said an Israeli military spokesman, Lt. Col. Peter Lerner.

In addition to the Hamas operatives, three others were killed in the Rafah strike, including a resident of the house and two neighbors, according to Palestinian health official Ashraf al-Kidra.

The neighbors were identified as Hassan and Amal Younis, the parents of Issam Younis, the director of Al Mezan, a leading human rights organization in Gaza.

At least 20 people, including four children — among them three brothers, and their father — were killed in 31 airstrikes across Gaza, according to al-Kidra.

Israel also hit at smuggling tunnels along the Gaza border with Egypt and at agricultural lands west of Rafah in Thursday’s airstrikes.

The military said 18 rockets and mortars were fired from Gaza since midnight Wednesday, compared to more than 210 over the previous 30 hours.

An Israeli was seriously wounded when a mortar hit south of the southern city of Ashkelon on Thursday, it said.

In a nationally televised address Wednesday, Netanyahu showed little willingness to return to the negotiating table after six weeks of war with Hamas.

“We are determined to continue the campaign with all means and as is needed,” he said, his defense minister by his side.