Splintered group that Abbas will have to take in hand

The Al-Aqsa Martyrs' Brigades, a rogue faction of which claimed responsibility for yesterday's suicide bombing, came into being during the current intifada. Unlike the Islamist groups Hamas and Islamic Jihad, it supports Yasser Arafat and the Palestinian Authority – except for a few splinter groups.

But with Israeli tanks and soldiers enforcing curfews in Palestinian cities in the West Bank and blocking Palestinians from travelling between, the al-Aqsa Brigades have fragmented, according to Palestinians.

The al-Aqsa Brigades were never a unified bunch but branches in individual cities are believed to have become virtually autonomous, with a single chain of command hard to maintain under Israeli military closures. It is in this climate that rogue factions such as the one in Nablus have begun openly to challenge the Palestinian Authority.

Until now, attention has focussed on the looming confrontation between Mr Abbas, who is expected to crack down on the militants, and Hamas, the most powerful of the groups. But Hamas has always been hostile to Mr Arafat and the PA. The divisions are clear-cut.

Much more dangerous is a possible confrontation now emerging: with the al-Aqsa Brigades. This would be a clash between the PA and militants who have strong links with Mr Arafat's Fatah movement.

The Israelis have accused Mr Arafat of directly controlling the al-Aqsa Brigades and ordering them to launch suicide bombings and other attacks. This accusation has never been proved and no convincing evidence has emerged.

A much more damning case against Mr Arafat is that he never publicly condemned the suicide bombings even when they were being committed by the al-Aqsa Brigades, which openly supported him as Palestinian leader.

But the links between the al-Aqsa Brigades and some individuals within Fatah are not in dispute. Some Fatah members of the Palestinian parliament have made clear they oppose Mr Abbas' plans to crack down on the militants, particularly the al-Aqsa Brigades, because they fear it could lead to "civil war".

When Mr Abbas made a deal with Mr Arafat over his cabinet, he emerged with Mohammed Dahlan, his new internal security minister, who is to crack down on militants.

But a few months ago it was Hani al-Hassan, the outgoing Interior Minister, who was promising to take on the militants. When he tried, publicly condemning a suicide bombing, the Nablus al-Aqsa Brigades openly threatened to kill him if he set foot in Nablus again. He called their bluff and went to Nablus, emerging alive. But Mr Dahlan is expected to do more than condemn bombings.