The tensions between the two main Palestinian factions erupted into open violence as hundreds of Hamas gunmen stormed a tribal bastion loyal to the rival, Western-backed Fatah movement in the Gaza Strip.

The fighting, which left at least 11 people dead and almost 100 wounded, was the worst since Hamas took control of the overcrowded coastal territory a year ago and marked a new low in efforts to resolve the increasingly complicated conflict.

The deterioration came days after Ehud Olmert, the Israeli Prime Minister, who had revived peace talks with the Fatah leadership in Ramallah, was forced to resign over widening corruption allegations.

With hatred flaring between Palestinians as never before, routed Fatah loyalists fled to the nearby Israeli border to seek refuge from the Islamists.

Israeli soldiers opened fire on Hamas gunmen attempting to shoot fellow Palestinians, survivors said.

Most of those escaping were members of the Fatah-affiliated Hilles clan, whose Sharjiyah neighbourhood was surrounded by as many as 800 Hamas fighters armed with machineguns and anti-tank rockets.

The Fatah fugitives were pinned down in hours of heavy fighting before fleeing a few hundred metres to the Israeli border. Many were wounded from the fighting or shot while trying to get away.

When Israeli troops eventually allowed them to cross, after pleas from the West Bank leadership, the men were strip-searched for arms before being sent to hospitals inside Israel.

The explosion in violence came as Hamas extended its crackdown on opposition groups in the Gaza Strip after a bomb attack on a café a week ago that killed four of its senior security officials and a young girl.

It has rounded up hundreds of people in reprisals and accused the Hilles clan of sheltering some of those behind the bombing.

In response, Fatah security forces in the West Bank arrested dozens of members of a non-violent Islamic party and enforced a new ban on public assembly.

The Ramallah leadership said that it would push for those wanted Fatah members who had fled Gaza to be relocated to the West Bank, but said that those with no fear of arrest would be returned to their homes in Gaza.

Yesterday about 30 were sent back to the territory, where they were immediately detained by Hamas forces for questioning.

Shadi Hilles, a 22-year-old former member of the Fatah security forces in Gaza, said that he wanted to stay in Israel and would be arrested and beaten by Hamas if he was forced to return. “I don't know what will happen. If I go back they are sure to get me,” he told The Times, lying with a foot wound in an Israeli hospital in Ashqelon.

There were a dozen other wounded Gazans, under guard by Israeli soldiers. “They arrest you, and they draw a tree or a ladder on the cell wall and tell you to climb it. When you can't, they beat you,” he said.

Mr Hilles said that, after a year of increasingly repressive rule by Hamas, people in Gaza were sick of being cut off from the world, and of Hamas's authoritarian Islamist government.

“Most Gazans hope Israel will re-invade Gaza after what they've been through,” he said. “We'd love to see the Israelis take out these people who harm their own people.”

He said that the Hilles clan had been expecting Hamas to turn its guns on them since the Islamist party forged a truce with Israel to stop firing rockets into the Jewish state.

With the outside foe at bay, Hamas turned on its internal rivals. “The only reason they succeeded was because some of the neighbours allowed them to dig tunnels into our area and surprise us in our sleep,” Mr Hilles said.

Ahmed Hilles, the tribal leader and senior Fatah member, who was shot in the leg fleeing the Hamas onslaught, said from his hospital bed in Beersheva in southern Israel: “Hamas will quickly discover it committed a very big act of stupidity that will be difficult to resolve.”

The deepening divide between the Palestinian factions in their separate entities has turned an already complex conflict into a Gordian knot.

Israeli media reported last week that Mahmoud Abbas, the Palestinian President in Ramallah, had threatened to dissolve his moderate Palestinian Authority if Israel released Hamas prisoners in exchange for an Israeli soldier captured by the Islamists two years ago on the Gaza border.

With Israel now facing months of political uncertainty in its own leadership, the rickety peace process appeared defunct yesterday. Nevertheless, Mr Abbas called on Egypt to broker talks with Hamas to discuss a solution to the clashes.

“We can't lose hope. We disagree and fight, but we have to work together to bridge the big gap created unfortunately by Hamas,” he said.

Factions at war

1964 Fatah, founded by Yassir Arafat with the aim of wresting Palestine from Israeli control, carries out its first military operation against Israel. By the end of the decade it effectively controls the Palestine Liberation Organisation

1972 Members of an extremist militant corps of Fatah called Black September murder 11 Israeli athletes at the Munich Olympics

1987 Hamas is founded as the Gazan arm of the Muslim Brotherhood, a religious and political organisation with branches throughout the Arab world. Its charter commits the group to the destruction of Israel and to raising “the banner of Allah over every inch of Palestine”

1993 Israel and the Fatah-led PLO sign the Oslo Accords. Hamas, which launched its first suicide attack this year, opposes the peace agreement

2005 Mahmoud Abbas, a Fatah founder, is elected Palestinian Authority President after the death of Arafat

2006 Hamas, which sponsors an extensive social service network, defeats Fatah movement in Palestinian elections

2007 Fatah and Hamas sign a deal that leads to a Palestinian unity Government, but Hamas later seizes the Gaza Strip from Fatah, prompting President Abbas to dismiss the administration

Sources: Times database; Council on Foreign Relations

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