JERUSALEM — Israel’s military said it launched an airstrike against militants in Gaza on Thursday, hours after a string of attacks on buses, civilian vehicles and soldiers left seven Israelis dead in the southern part of the country.

The action targeted top leaders of the Popular Resistance Committees in Gaza who were behind the attacks with the intention of kidnapping an Israeli civilian or soldier, the Israel Defense Forces said.

The airstrike occurred just west of Rafah, close to the Egyptian border, and killed six people, Palestinian medical and security sources said. The victims were five Popular Resistance Committees members and the son of one of the the members.

Kamal Nirab, head of the group in Gaza; Imad Hamed, head of its military wing; and Khaled Shaat, a senior operative, were among those targeted, the IDF said.

“IDF’s blows are now hitting the heads of the committees in Gaza,” Israeli Defense Minister Ehud Barak said.

Hours earlier, six civilians and one Israeli soldier were killed and 40 people were wounded in attacks about 20 kilometers (12 miles) from the Israeli city of Eilat, close to the Israeli-Egyptian border. Israeli soldiers exchanged gunfire with the assailants and killed seven militants, the military said.

Israel believes that the attacks had their roots in Gaza but were coming out of the neighboring Egyptian region of Sinai. They come amid what Barak says is “the weakening of Egyptian control over Sinai.”

“We were all witness today to an attempt to go up a scale in the terror front by committing attacks out of Sinai,” Israeli Prime Minister Benjamin Netanyahu said.

“The people who gave the order to murder our citizens and that were hiding in Gaza are no longer alive. If the terrorist organizations think that they can hurt our citizens, they will soon find out that Israel will have them pay a price, a very heavy price.”

Hamas denied responsibility for the strikes and condemned “the crime in Rafah.” It claimed that Israel was looking for a pretext to attack Gaza and warned of reprisals.

Ihab Al Ghosen, a Hamas spokesman, said the Interior Ministry “announced a state of emergency and told the people to be careful and take all the measures needed, hospitals are on high alert, and concentrations of security forces were evacuated.”

Abu Suhayb, the spokesman for the Popular Resistance Committees, denied involvement in the Eilat attack. The group said it would have announced its involvement if it were responsible.

“We warned Israel not to blame us just because it is easy for them to do so,” he said. “All the options are open now for reaction, from kidnapping soldiers, to suicide attacks inside Israel and to shelling with rockets.”

Israel had been on heightened alert in the south of the country, and an elite counter-terrorism unit was in the area, according to an Israeli government source who doesn’t want to be identified because he cannot speak publicly about the matter. The counter-terrorism unit and Israeli soldiers responded to the attacks, the source said.

The incident began when shots were fired at a civilian bus traveling from Be’er Sheva to Eilat, near the community of Netafim. Attackers also fired shots at another bus and two civilian vehicles.

Officials say it’s likely there were both civilians and active-duty soldiers traveling by bus in the area because it was the start of the weekend and soldiers might have been going on breaks to the Eilat area.

There were casualties in both incidents, the IDF said. Civilians and soldiers were among the casualties.

Later, IDF soldiers were injured when an explosive device was detonated as they arrived on the scene.

Several mortar shells “were simultaneously fired from the Gaza Strip at soldiers conducting routine maintenance work on the security fence on the Israel-Egypt border.” That was a bit farther north along the border from the bus attack, the IDF said.

“This is a malicious attack on innocent civilians, who were on their way to the known tourist destination city, Eilat, for their summer vacation,” the IDF said. “The IDF will pursue those responsible for this attack at all costs and will not allow any further harm to Israeli civilians.”

Barak said Israel “will not always be able to prevent such attacks.”

“The Egyptian control over Sinai is weakening, and this is probably the reason that this attack that originated in Gaza has made it all the way down here.”

He said the IDF “will continue to work in full force and protect the normal life in the city of Eilat.”

Netanyahu and Barak met to discuss the “grave attacks,” the prime minister’s office said.

“In light of what’s happening near Eilat, our deepest condolences go out to the victims, their families and loved ones, of what appears to be a brutal and cowardly act of terrorism in southern Israel,” the U.S. Embassy in Tel Aviv said.

“We wish those injured a speedy recovery. The American people and the Israeli people stand united against terror and we hope that those involved in the planning of this gruesome attack will be brought to swift justice.”

Eilat is a resort town on Israel’s southern tip, near Egypt’s Sinai border. It generally has not endured the kind of strife faced by other regions including the swath of southern Israel near Gaza, the coastal Palestinian territory just south of the Jewish state along its west coast.

Across the border, the Egyptian army and police are cracking down in an “anti-terror” operation in the Sinai area of Egypt, state-owned media reported Tuesday, as reports emerged of Osama bin Laden’s doctor surfacing in the area.

Police said they found hand grenades, machine guns, rocket-propelled grenades and ammunition in the operation that targets Sinai “terror cells” suspected in attacks on a gas pipeline to Israel and a police station in the border town of el-Arish.

One person was killed and 12 were arrested Monday, the first day of the operation, said Hazem al-Maadawi, a police officer involved in the offensive.

Netanyahu told a Knesset committee recently that Egypt was having difficulty exercising its sovereignty over Sinai.

“What’s happening in Sinai is that global terrorist organizations are meddling there and their presence is increasing because of the connection between Sinai and Gaza,” Netanyahu said.

Questions are being raised about the Egyptian military presence in the demilitarized zone in Sinai, which was created under the terms of the Camp David Agreement signed in 1978 between Egypt and Israel.

CNN’s Kevin Flower, Michal Zippori and Guy Azriel contributed to this report