Saboteur bombers on Wednesday destroyed the two minarets of the Shiite holy shrine of Askariya in Samarra, in a repeat of a 2006 bombing that shattered its famous Golden Dome and unleashed a wave of retaliatory sectarian violence that still plagues Iraq
Police said the attack at about 9 a.m. (0500gmt) involved explosives and brought down the two minarets, which had flanked the dome's ruins. No casualties were reported.
Sunni extremists of al-Qaida were quickly blamed, and the attack immediately stirred fears of a new explosion of Sunni-Shiite bloodshed.
Meanwhile in Iraq, streets in the centre were almost deserted, except for US military patrols and Iraqi police, as a curfew was enforced following the Samarra shrine attack.
The repeat assault on a revered Shiite shrine immediately stirred fears of a new explosion of intra-Muslim bloodshed, and prompted the 30-member bloc of radical Shiite cleric Muqtada al-Sadr to suspend its membership in Iraq's parliament, threatening a deepened political crisis.
To try to ward off an upsurge in Iraq's unending violence, Prime Minister Nouri al-Maliki quickly imposed a indefinite curfew on vehicle traffic and large gatherings in Baghdad - at first set for 3 p.m. (1100gmt) on Wednesday, later delayed to (1400gmt) 6 p.m.
It wasn't clear how the attackers evaded the shrine's guard force to mount the stunning operation, detonating the
blasts around 9 a.m., and bringing down the two slender golden minarets that flanked the dome's ruins at the
Policemen at the shrine were subsequently detained and will be questioned as part of the investigation, al-Maliki
In addition to ordering the curfew, al-Maliki's office said, the Iraqi leader met U.S. Iraq commander General
David Petraeus and U.S. Ambassador Ryan Crocker to ask that American reinforcements be sent into Samarra, 95 kilometres (60 miles) north of Baghdad, and U.S. troops in the capital be put on heightened alert.
Al-Maliki later, in a nationally televised address, said he had ordered security forces to beef up protection of
religious shrines and mosques across Iraq.
The Shiite prime minister also warned against reprisal sectarian attacks.
An unnnamed official close to the prime minister, citing intelligence reports, said Wednesday's bombing was likely the work of al-Qaida, whose militants have recently moved into Samarra from surrounding areas.
Black banners were hoisted outside the Najaf residence of radical Shiite cleric Muqtada al-Sadr, who called for a three-day mourning period to mark the minarets' destruction.
The cleric, who criticised the government for not doing enough to protect the site, also called for peaceful demonstrations following the blasts.