Hamas ends ceasefire after Israeli attack kills family

The military wing of Hamas responded by ending the fragile ceasefire it has maintained for the past 16 months. "We are going back to work, to fight," it said in a press statement. "The earth will shake in the Zionist cities. The only choice for these settlers will be to pack up and leave."

Mahmoud Abbas, the Palestinian President, condemned the killings as a "bloody massacre", but the Hamas political leadership was slow to endorse its military wing's announcement.

Lt-Gen Dan Halutz, the Israeli Chief of Staff, suspended the shelling from land and sea, which had continued throughout the day in retaliation for Palestinian rocket fire into the Negev. Four rockets fell there yesterday, damaging property but causing no casualties.

The army apologised for the incident, saying it "regretted the strike on innocent people". Maj-Gen Yoav Galant, the chief of southern command, ordered an investigation. "It is not our intention to harm innocent civilians," he said. One possibility, he suggested, was that a shell had strayed from its path. Israel was also checking whether the disaster was caused by what they call a "work accident" - a Palestinian bomb exploding prematurely.

But Maj-Gen Galant insisted that, despite the pause, the army would continue to do everything to defend its own civilians, who have come under incessant attack from Qassam rockets launched across the border from the Gaza Strip. Two sonic booms shook Gaza City later last night.

Amir Peretz, the Defence Minister, expressed his regret at the loss of civilian lives. "We don't seek to fight against the Palestinian people, only against terror," said the Labour Party leader, whose home town of Sderot has borne the brunt of the Qassam shelling.

Earlier yesterday, an Israeli air strike killed three gunmen. A military spokesman said they were hit minutes after firing a Qassam rocket into Israel. One was standing beside a car; the other two were trying to drive away. They were hit by a second missile.

Israeli forces had been alerted after Palestinian militants vowed to avenge Thursday night's killing of Jamal Abu Samhadana, who headed the Hamas government's security forces in the Gaza Strip and the umbrella Popular Resistance Committee. He was the first office-bearer assassinated by Israel since Hamas came to power in January.

More than 10,000 mourners attended the funeral of Mr Abu Samhadana, who died along with at least three other members of the resistance committee when warplanes hit a military training camp.

Abu Abir, a resistance committee spokesman, said the Israelis had "opened the gates of hell" by his assassination. "The Zionist entity and Zionist settlements near Gaza will not feel security and safety any more," he said. "Our rockets will rain into the Zionist entity and our heroes will blow themselves up among their dirty bodies."

Israel accused Mr Abu Samhadana of ordering many of the rocket attacks, which have pounded the Negev since Israel withdrew from Gaza last August. He is also suspected of masterminding a roadside bombing that killed three security men escorting an American embassy aid convoy in 2003.