JERUSALEM, Aug 18 (Jeffrey Heller/Reuters) - Gunmen killed seven people in southern Israel on Thursday in attacks along the Egyptian border and Israel responded with an air strike in the Gaza Strip that killed six Palestinians, including the leaders of a group it blamed for the violence.
The series of assaults on a desert road north of Israel's Red Sea resort of Eilat drew Israeli accusations that Egypt's new rulers were losing their grip on the porous frontier.
Israel said the attackers infiltrated from the Hamas-run Gaza Strip via Egypt's Sinai desert, despite stepped up efforts by Egyptian security forces in recent days to rein in Palestinian and Islamist radicals.
If anyone thinks the State of Israel will resign itself to this, they are wrong, Prime Minister Benjamin Netanyahu said in a brief television address about the most deadly attack in Israel since 2008.
Israeli commanders said six civilians and one soldier were killed in attacks on two buses, a car and an army vehicle. Another 25 people were wounded.
The violence, which began in the early afternoon, stretched into the evening. As the Israeli military's chief of staff and Defense Minister Ehud Barak were briefing media at the scene, ambulances raced away to what reporters said was another attack by gunmen in which two people were wounded.
The military said seven gunmen were killed in southern Israel, including two who blew themselves up in suicide attacks on one of the buses and in a confrontation with soldiers.
Egyptian soldiers apparently shot dead two gunmen, the military said.
Hours later, Israel struck against the Popular Resistance Committees, an armed faction that often operates independently of Gaza's Hamas rulers. The Israeli military said the PRC was behind the border attack -- a charge denied by the faction.
The PRC said its commander, Kamal al-Nairab, his deputy, Immad Hammad, and three other members were killed in the Israeli air strike on a home in the southern Gaza town of Rafah.
The faction vowed revenge for the attack, which hospital officials said also killed a two-year-old son of the owner of the house. Locals earlier gave the boy's age as nine.
The people who gave the order to murder our people and hid in Gaza are no longer among the living, Netanyahu said on television. I set a principle: when someone harms the citizens of Israel, we react immediately and with force.
Earlier, in an interview with Israel Radio, bus driver Benny Bilbaski said he had seen two men in fatigues shooting at his vehicle.
I saw that there were wounded on the bus but I continued to drive on, looking straight, not looking right or left. Once I got a kilometer past the area and I was out of range we took care of the wounded, he said.
Barak said the incident reflects the weakening of Egypt's hold in the Sinai and the broadening of activities by terror elements.
A senior Israeli official said the gunmen, unable to cross into Israel through the heavily patrolled border with Gaza, had gone into the Sinai and then infiltrated from there into Israel.
In Washington, U.S. Secretary of State Hillary Clinton issued a statement denouncing the brutal and cowardly attacks near Eilat. She said the violence only underscores our strong concerns about the security situation in the Sinai Peninsula and urged the Egyptian government to find a lasting resolution.
Israeli officials have voiced concern that militant groups in the Sinai have been making use of a security vacuum left by the overthrow of Egyptian President Hosni Mubarak in February.
The Israeli shekel fell against the dollar and stocks dipped on Thursday. The violence appeared to take some domestic political pressure off Netanyahu: leaders of escalating protests against high living costs called off weekend demonstrations after news of the Israeli casualties broke.
Egypt, which signed a peace treaty with Israel in 1979, recently stepped up security activity in the Sinai.
On Tuesday, Egyptian security sources said an army crackdown on armed groups in the northern Sinai had netted four Islamist militants as they prepared to blow up a gas pipeline.
Israel is building a fence along its 180-km-long frontier with Egypt, but very few sections have been completed.
The PRC said it was not involved in the attacks in southern Israel. After dark, it launched a rocket across the border which Israel said was shot down by an air defense system.
The Zionist enemy committed a grave mistake by assassinating our leaders and they will pay a heavy price for it, PRC spokesman Abu Mujahed said. (Additional reporting by Yusri Mohamed in Ismailia, Egypt, Nidal al-Mughrabi in Gaza and Dan Williams in Jerusalem; Editing by Maria Golovnina and Rosalind Russell)