It was imposed on Thursday amid clashes between troops and Shia militias in Baghdad and elsewhere, and was due to expire early on Sunday morning.

The news came hours after radical Shia cleric Moqtada Sadr's Mehdi Army militia said it would defy a government call to lay down its weapons.

Across Iraq, fighting has claimed an estimated 200 lives since Tuesday.

The BBC's Crispin Thorold in Baghdad says the curfew extension will damage the capital economically, as well as inconveniencing residents.

The initial imposition of the curfew was a sign of how badly security in Baghdad had deteriorated, he says.

Baghdad, particularly the Shia-dominated Sadr City area in the east of the city, has seen some of the worst violence in recent days, including a series of US air strikes on Friday.

Air strikes

The curfew extension came after a day of skirmishes between security forces and Shia militiamen in the southern city of Basra, where the current wave of unrest began.

Fierce gun battles were reported, while the UK military said US warplanes carried out two air strikes.

Iraqi police said an earlier US air strike killed eight people, although no independent confirmation was available.


Iraq map

Turkey hits rebel targets
British forces in the city fired artillery rounds on what they said were militia mortar positions - the first time they had directly joined the fighting since government forces launched an operation in Basra on Tuesday.

Iraqi forces have been trying to wrest control of the city and other Shia areas from the Mehdi Army.

Haider al-Jabari, a senior Sadr official in the city of Najaf, confirmed the militiamen had been ordered not to lay down their arms, as demanded by Prime Minister Nouri Maliki.

"Sadr has told us not to surrender our arms except to a state that can throw out the [US] occupation," he told AFP news agency.

On Friday Mr Maliki extended an original three-day deadline, telling the fighters they had until 8 April to hand in their weapons in return for cash.

On Saturday the prime minister vowed that government troops will not leave Basra until "security is restored", describing the gunmen as "worse than al-Qaeda".

A man inspects a charred Iraqi army vehicle in Basra on 29 March
Iraqi soldiers have met fierce resistance in Basra
"We will continue to stand up to these gangs in every inch of Iraq," he said.

Meanwhile Al-Jazeera TV broadcast excerpts from an exclusive interview with Moqtada Sadr that it conducted hours before the beginning of the clashes on Tuesday.

Mr Sadr called on Arab and Muslims states and the UN to "recognise the legitimacy of resistance" and offer support to Iraqi to "drive the occupation forces out of its land".

Power struggle

Estimates vary of the number of deaths since the fighting broke out. Health officials in Baghdad say at least 75 people have been killed in the city in five days.

In Basra, the British military say 50 people have been killed, although local medical sources report as many as 290 dead.

The fighting, which has spread from Basra to Baghdad and other towns such as Hilla and Nasiriya, is blamed on a power struggle between rival Shia factions.

Moqtada Sadr's followers have in the past rebelled against the US-backed government, although the cleric's political bloc has backed Mr Maliki's ruling coalition.

A ceasefire by the Mehdi Army, in place since August 2007 and renewed in February, has been widely credited with reducing sectarian tensions and contributing to the recent overall drop in violence.

Correspondents say Moqtada Sadr's supporters fear the prime minister - also a Shia - wishes to weaken their movement before local elections due later this year.

In separate developments on Saturday:

* Two US soldiers were killed in eastern Baghdad, the US military said

* Turkey said it had killed 15 Kurdish rebels in northern Iraq in cross-border shelling on Thursday, and carried out air strikes in the area on Friday.