Hamas said that an Israel airstrike in Gaza killed three of its senior military leaders early Thursday.
The Palestinian militant group claimed that the men -- identified as Mohammed Abu Shamaleh, Mohammed Barhoum and Raed al-Attar -- were killed along with three other people in a strike on a four-story building near Rafah, a town in the southern part of the coastal territory.
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.
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.
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. Hamas' 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 strike was the result of intelligence and operational activities, which led to the detection and attack on two central operatives from the heart of Hamas’s military leadership," Israeli security agency Shin Bet said in a statement.
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 strike, one of 20 the Israeli military said it carried out early Thursday, came one day after another strike in Gaza City aimed at Hamas' senior military leader, Mohammad Dief. Israeli intelligence sources have told Fox News that they believe that Dief was killed in that operation, but Hamas has claimed that he survived.
Israel says the airstrikes are in response to a resumption of Hamas rocket fire Tuesday that scuttled a six-day cease-fire.
Since Tuesday, 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 an Egyptian cease-fire 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 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.
The Associated Press contributed to this report.