Israel pounds Gaza after deadly attacks near Eilat
The Israeli military has carried out air strikes over the Gaza Strip, targeting those it blamed for a series of deadly attacks in southern Israel.
At least six people, including a senior militant, were killed in the air strikes, Palestinian sources said.
Earlier, Israeli officials promised a strong response after attacks on vehicles near Eilat left seven dead.
Israeli officials said Gazan militants were responsible, although Gaza's Hamas government denied involvement.
The Israeli air strike hit a house in the town of Rafah.
Palestinian sources told the BBC that four members of the Popular Resistance Committees (PRC), a faction in Gaza that is loyal to Hamas but sometimes operates separately, had been killed in the air strikes, including the group's head, Kamal al-Nairab.
PRC military chief Immad Hammad and the son of the owner of the house were also among those killed, Palestinian sources and residents said.
Israeli Prime Minister Benjamin Netanyahu said those killed were responsible for the attacks earlier in the day near Eilat.
"The people who gave the order to murder our people and hid in Gaza are no longer among the living," he said in a televised address.
"If anyone thinks the state of Israel will resign itself to this, they are wrong."
The PRC denied involvement in the attacks in Israel, Reuters reported.
Further air strikes took place in the early hours of Friday morning.
'Risk of escalation'
A spokesman for Israel's domestic security agency, Shin Bet, said several of those who died in the air strikes had been involved in the 2006 capture of Israeli soldier Gilad Shalit.
Hamas-run Al-Aqsa television reported that security forces in Gaza had evacuated their headquarters in anticipation of Israeli military action.
The attacks near Eilat, a southern resort city, began when gunmen opened fire on a bus.
Israeli officials said at least two other vehicles were then hit nearby - one by a rocket and one by an explosive device.
They said that the attacks left seven Israelis dead and that a number of gunmen were killed in an ensuing firefight.
In response, Israeli Defence Minister Ehud Barak said: "The real source of the terror is in Gaza and we will act against them with full force and determination."
Hamas, which governs Gaza, denied responsibility, and said it would retaliate if Israel attacked.
"We will not stand handcuffed and we will spearhead resistance to the occupation," Hamas official Salah Al-Bardaweel was quoted as saying.
The US, the EU and the UN condemned the attacks in Israel.
"We condemn the brutal terrorist attacks in southern Israel today in the strongest terms," the White House said in a statement.
A UN spokesman said Secretary-General Ban Ki-moon was "concerned at the risk of escalation and calls for all to act with restraint".
Israeli officials said the men who attacked the vehicles near Eilat came from the Gaza Strip and had entered Israel through Egypt's Sinai desert.
There has been growing concern about a decline in security in Sinai since Egyptian President Hosni Mubarak was toppled in February.
"This violence only underscores our strong concerns about the security situation in the Sinai Peninsula," said US Secretary of State Hillary Clinton.
"Recent commitments by the Egyptian government to address the security situation in the Sinai are important and we urge the Egyptian government to find a lasting resolution."
An Israeli official said gunfire on either side of the border was continuing into the evening.
Late on Thursday, Egyptian officials said at least two Egyptians were killed near the border in northern Sinai.
Details of the deaths were unclear, though there were reports that gunmen had attacked a police post.