Gunfights and mass-arrests swept the Palestinian territories over the weekend in the aftermath of a deadly bomb attack on Gaza’s Hamas rulers, which the Islamists blamed on their western-backed rival Fatah.

A major Hamas security sweep in Gaza, in which hundreds of Fatah members were rounded up for interrogation and the movement’s offices shut down, triggered fighting involving another group, the Army of Islam, a radical, smaller movement with previous links to both factions and which kidnapped Alan Johnston, the BBC journalist.

In the middle of the internal fighting, Israeli forces simultaneously launched a raid to arrest a senior Hamas fugitive in the southern West Bank city of Hebron, killing the man when he opened fire on the raiding party.

The violence erupted on Friday evening when a bomb exploded at a Gaza beach café, killing five high-ranking Hamas officials and a five-year-old girl. Hamas quickly accused Fatah, which it has blamed for several bombings and assassination attempts since the secular group lost control of Gaza to the Islamists in battle last summer.

Hamas police flooded the streets and conducted a number of raids, arresting around 200 people linked to Fatah, whose leader, Mahmoud Abbas, is the Palestinian President.

Hamas gunmen also shut down scores of Fatah-run sports and cultural clubs, as well as the regional Fatah headquarters offices in the coastal strip’s towns. The security forces confiscated computers and documents as part of the crackdown

In response, Fatah – now in nominal control only of the West Bank, which is still occupied by the Israeli military – carried out a series of tit-for-tat arrests in northern West Bank towns of Jenin and Tulkarem, detaining 35 Islamists.

Hamas’ wide-ranging security crackdown in Gaza also sparked armed clashes with the Army of Islam, a group which claims to have links to al-Qaeda. The small movement, headed by Mumtaz Doghmush, helped Hamas capture Gilad Shalit, an Israeli soldier, in a cross-border raid two years ago before running foul of Gaza’s new rulers over its three-month detention of Mr Johnston.

The Army of Islam is based in a cramped area of southern Gaza City dominated by the powerful and fiercely territorial Doghmush clan, with whom Hamas has had run-ins in the past over smuggling operations. Hamas policemen fought gun battles with clansmen and militia members for hours, at one point having to extricate a group of its policemen who were pinned down by Doghmush snipers. At least three people were wounded in the all-night clashes.

Following the infighting, Israeli forces stepped into the complex melee this morning with a raid to nab the senior Hamas militant, Shihab al-Natsheh, whom Israel accused of masterminding a suicide bombing in the southern Israeli town of Dimona in February, killing an elderly Israeli woman.

Israeli troops killed the 25-year Hamas bomb-maker in Hebron after he reportedly opened fire on them. Hamas, which has been observing a fragile truce with Israel to halt rocket-fire from Gaza, promised to hit back for Mr al-Natsheh’s killing.

"Our response will be swift and painful," said the group’s armed wing in a statement.

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