Sectarian violence claimed more than 130 lives across Iraq yesterday despite calls for calm from leaders fearful of all-out civil war.

A day after a suspected al-Qa'eda bomb destroyed a major Shia shrine, leave was cancelled for the police and army. Minority Sunni political leaders pulled out of US-backed talks on forming a national unity government, accusing the ruling Shias of fomenting dozens of attacks on Sunni mosques.

The attacks showed a precision and brutality exceptional even in Iraq. At a makeshift checkpoint outside Baghdad, gunmen dragged drivers from their cars to be shot. In all, 47 bodies - all Shias who had been demonstrating against Wednesday's bombing of the Golden Mosque in Samarrah - were found in a ditch near the village of Nahrawan.

In the capital, more than 80 bullet-ridden corpses were taken to the mortuary in the 24 hours after two explosions destroyed the gold-plated dome of the 1,200-year-old mosque. Most were Sunnis.

Seven more people died in fighting between Shia militiamen and Sunni gunmen in Mahmoudiyah, south of the capital, while in Baquba a bomb killed at least 16, though its intended target may have been an Iraqi army patrol.

In Samarrah, three Iraqi journalists working for the Al-Arabiya television channel were seized by gunmen and murdered.

Mass demonstrations by Shias continued, with thousands protesting in Baghdad, Karbala, Kut, Tal Afar and Najaf. In Najaf, religious leaders called on people to go to Samarrah to defend the shrine from any further violation.

Fears are growing that unless the government can reassert some form of control the country will descend into an irreversible sectarian conflict. A curfew was extended for a further two days in Baghdad and Salaheddin, the province north of the capital in which Samarrah is located.

There is also concern that the true number of those so far killed already far exceeds the official numbers. Shias form the majority in Iraq, and are enjoying dominating government after suffering under the dictatorship of Saddam Hussein, a secular Sunni.

The two branches of Islam are separated mainly by Shia belief that Imam Ali, a cousin of Mohammed, is second in importance to the Prophet. Over the centuries, differences in practice and spiritual belief have hardened.

Sectarian killings are not new following the American-led invasion but what is happening now appears unprecedented in its scale and systematic nature.

One driver, Hussein Ali, told how he had been stopped by gunmen at a checkpoint in Baghdad and asked if he was Shia or Sunni. He was Shia so allowed to go on.

Nearby, a 55-year-old Sunni woman was killed when gunmen descended on her home. Neighbours begged the men to spare her but she was shot three times in the head after they pronounced her "a Sunni from Samarrah".

Moqtada al-Sadr, the militant cleric whose black-shirted Mahdi army has been the most prominent of all the Shia armed groups warned that the government and US had failed to protect the Samarrah shrine and ordered his followers to defend all Shia holy sites.

Mahmoud Ahmadinejad, the president of Iran, the only Shia state, warned Western powers that they would face the wrath of Muslims following the devastating bombing.

"These heinous acts are committed by a group of Zionists and occupiers that have failed," Mr Ahmadinejad said in a speech broadcast live on state television.

The Association of Muslim Scholars, a hardline Sunni body, claimed 168 Sunni mosques had been attacked, 10 imams killed and a further 15 abducted.

It called on Sunnis to do what they must to protect themselves.

The Iraqi government said that in Baghdad only 19 mosques had been attacked, while the US military put the national figure at seven.

But whatever the reality the growing atmosphere of fear meant in many districts

Sunnis appeared to be heeding the call to look to their own defence.

• Seven US soldiers died yesterday in roadside bombings in the towns of Balad and Hawija.

23 February 2006: Shias take bloody revenge for attack on shrine

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