BAGHDAD Suspected al Qaeda militants on Wednesday blew up the minarets of a revered Shi'ite mosque in the Iraqi city of Samarra, target of a 2006 bomb attack that unleashed a tidal wave of sectarian violence.
Fearing renewed bloodshed, Iraq's government imposed a three-day curfew in Baghdad as Shi'ite and Sunni political and religious leaders called on their followers to remain calm.
But police said gunmen blew up the Sunni Grand Mosque in Iskandariya, south of Baghdad, destroying it. A second was damaged in another blast and attackers set fire to a mosque in Baghdad's Bayaa district. No injuries were reported.
A grim mood descended on the capital as people hurried home before the start of the curfew. The streets were largely empty apart from patrolling Iraqi police and soldiers.
Shi'ite Prime Minister Nuri al-Maliki and other Iraqi leaders met the top U.S. military commander in Iraq, Gen. David Petraeus, and U.S. Ambassador Ryan Crocker, agreeing on political and military steps aimed at "promoting restraint," U.S. officials said.
U.S. President George W. Bush called Maliki to offer his condolences over the attack, which he described as "barbarous," and to urge Maliki to "turn this moment of tragedy into opportunity" by showing unity against militants.
U.S. military spokesman Brig. Gen. Kevin Bergner said Maliki had ordered the deployment of an extra Iraqi brigade to Samarra while investigators tried to establish how the bombers managed to stage an apparent repeat of the February 22, 2006, attack on the al-Askari mosque that collapsed its famed golden dome.
That bombing was a turning point for Iraq, lifting the lid on simmering tensions between Shi'ites and Sunni Arabs. The two sects are now locked in a cycle of violence that has killed tens of thousands and forced nearly 2 million to flee the country.
Iraq's leaders have often voiced fears a repeat of the 2006 attack could trigger all-out sectarian civil war.
The U.S. State Department said Washington was concerned about the potential affect of Wednesday's attack "among various groups within Iraq." In a joint statement, Petraeus and Crocker called on Iraqis to "reject this call to violence."
In a televised address, Maliki also blamed al Qaeda for the attack and called on Iraqis to unite. He said he had ordered the arrest of the policemen who had been guarding the mosque and his office said he had visited the scene.
Also on Wednesday, the U.S. military said it killed al-Qaeda in Iraq's military leader for the city of Mosul, Kamal Jalil Bakr Uthman, who was known as Sa'id Hamza.
Sa'id Hamza, who planned suicide bombings in Mosul, was slain by troops when he apparently reached for a suicide vest after they entered his house on Tuesday during an operation targeting al-Qaeda in Iraq, U.S. Central Command said in a statement.
The attack on the Samarra mosque comes at a critical time in Iraqi politics. Maliki's government is under growing pressure to move faster in passing key laws U.S. officials hope will draw Sunni Arabs closer into the political process and undermine the insurgency.
But there has been almost no progress and there are signs a major U.S.-Iraqi crackdown in Baghdad aimed at buying time for Maliki's government is running out of steam. The number of death-squad killings has begun to rise in the city.
The political bloc of fiery anti-American cleric Moqtada al-Sadr, whose Mehdi Army militia is blamed for fueling the violence, urged its supporters to remain calm but said it was suspending its participation in parliament in protest.
There were no injuries reported in the attack on Samarra's Golden Mosque, which demolished its two 36-metre- (118-foot) high golden minarets. It had been closed since 2006 due to disagreements between Shi'ites and Sunnis over its reconstruction.
The U.S. military, quoting police at the scene, said they were destroyed in near simultaneous explosions heard coming from inside the mosque compound. Bergner said it appeared some form of explosives had been used.
The Golden Mosque is one of the four major Shi'ite shrines in Iraq. Samarra, north of Baghdad, is a predominantly Sunni city. Other major sites are in the holy Shi'ite cities of Najaf and Kerbala and the Baghdad district of Kadhimiya, also mainly home to Shi'ites.
(Additional reporting by Waleed Ibrahim and Alister Bull, and David Alexander and Caren Bohan in Washington)