The targeting of both Israel and the United Nations served as a double blow to the crumbling authority of Palestinian leader Mahmud Abbas, who had issued a desperate appeal to tackle what he acknowledged was a state of anarchy.

The main Palestinian factions had signed up to a truce brokered by Abbas in March, agreeing to "cool down" their campaign of attacks against Israel at least until the end of the year.

Abbas had strong hopes that the militants would agree to extend the truce but a recent upsurge in rocket attacks, prompting Israel to reassert control over parts of the northern Gaza Strip, had illustrated that its days were numbered.

Confirmation that the factions no longer feel bound by the so-called "tahdiya" came with statements from three groups, which claimed credit for a series of rocket attacks into Israel.

The Al-Aqsa Martyrs Brigades and the armed wing of Islamic Jihad said in a joint statement they had fired two rockets at the southern Israeli town of Sderot while the Popular Resistance Committees said in a separate statement it had fired rockets at army posts and at a kibbutz in Israel.

An Israeli military spokeswoman confirmed that rockets had been launched but said there were no reports of them hitting their targets.

"Several launches were identified but nothing landed inside Israel," she told AFP.

The armed wing of Hamas, responsible for the majority of attacks during the five-year uprising, also confirmed that it was ending its adherence to the truce.

The resumption of attacks by Al-Aqsa, a group nominally loyal to the ruling Fatah faction, is particularly embarrassing for Abbas and highlights the deep divisions within the movement which had huge problems just on agreeing a list of candidates for parliamentary elections on January 25.

Abbas has been a consistent critic of rocket attacks and has urged the factions to stop regarding themselves above the law.

Rather than reverse a tide of lawlessness since Israel left Gaza in September, Abbas has presided over a worsening of the chaos.

Foreign aid workers based in Gaza have increasingly become targets of the wrath of disaffected youngsters drawn to the armed factions.

A recent spate of kidnappings has prompted the United Nations to withdraw all but a handful of its foreign staff.

However the organisation was still the target of a gunmen overnight who stormed the UN beachfront club, beat up a lone security guard on duty and then detonated a number of hand grenades, according to Palestinian security sources.

The UN club, which overlooks the Mediterranean, is the only place which serves alcohol in the territory.

While thousands of Palestinians are employed by the United Nations in Gaza, the number of international staff has been slashed in recent months as a result of the mounting security crisis.

A UN source told AFP that the club had not been open for New Year celebrations as only three international staff remain in the territory.

"All but three foreign staffers have left Gaza and they are under strict orders not to leave their base after nightfall," said the source.

The attack came only a day after the end of the latest hostage drama in Gaza when a British rights worker and her parents were freed, more than 48 hours after being abducted.

Despite repeated pledges, Abbas has failed to tackle the lawlessness of Gaza where gunmen, operating in the name of "resistance" to Israel, act above the law.

In a speech marking the 41st anniversary of Fatah, Abbas warned that the violence was playing into the hands of Israel and undermining the Palestinian dream of statehood.