Iraq cancelled all leave for the police and army and placed them on the highest alert as the death toll mounted yesterday in sectarian violence that has swept the country after bombs wrecked a major Shi?ite shrine.

A crisis summit called by the president to halt a descent to all-out civil war was thrown into doubt when the biggest Sunni political group boycotted it in protest at what it called the Shi?ite-led government?s failure to protect Sunni mosques.

The leading Sunni religious body accused Shi?ite clerics of fuelling the violence; the comments by a spokesman for the Muslim Clerics Association were a rare, if veiled, attack on Grand Ayatollah Ali al-Sistani, a revered figure for majority Shi?ites who has called for protests but also restraint.

Police and military sources tallied at least 78 deaths, mostly of Sunnis, in the two biggest cities, Baghdad and Basra, in the 24 hours since suspected al Qaeda bombs devastated the Golden Mosque in Samarra, one of Shi?ite Islam?s holiest sites.

Washington, which wants stability in Iraq to help it extract around 130,000 troops, called on Iraqis to prevent spiralling sectarian violence. US forces have been in Iraq since they led a 2003 invasion to topple Saddam Hussein.

Curfew

The Interior Ministry said all police and army leave was cancelled, curfews were extended as the country locks down for three days of national mourning and forces were on high alert. Dozens of Sunni mosques were fired on by gunmen and a few were destroyed by fire. A bomb blasted an Iraqi army foot patrol in a market in the religiously divided city of Baquba, killing 16 people, including eight civilians, and wounding 21.

Three Sunni mosques were ablaze yesterday in the mixed neighbourhood of New Baghdad, in the south of the capital.

It was not clear if the total of 53 deaths in Baghdad included over 40 bodies found at a nearby village which has seen previous attacks on Sunni residents by Shi?ite militiamen.

Nor was it clear if the Basra death toll of 25 included up to 11 Sunni rebel suspects hauled from a prison overnight by men in police uniform and left shot dead in various parts of the mainly Shi?ite southern city.

Three journalists working for Al-Arabiya television were found shot dead after being attacked while filming in Samarra, where the bloodless but highly symbolic bombing of the Golden Mosque at dawn on Wednesday provoked widespread protest.

?The leadership of the Iraqi Accordance Front has sent its apologies to the president to say they will not attend today?s meeting,? senior Front official Iyad al-Samarrai told Reuters, announcing the boycott by the main Sunni Arab political group.

?The government neglected to provide security for our sites ... They did not condemn these acts of aggression.?

Another Front spokesman said it could suspend participation in U.S.-sponsored talks to form a national unity coalition.

President Jalal Talabani, an ethnic Kurd, had called the meeting at his residence in an effort to ease tensions which he warned on Wednesday?s could lead to a ?devastating civil war?.

It was not clear if broader talks would now go ahead without the presence of the Accordance Front, which includes the Iraqi Islamic Party. The Front won 44 of 275 seats when the once dominant Sunni minority ended its boycott of the US-sponsored political process and took part in an election in December.

Al Qaeda

US Secretary of State Condoleezza Rice, who is visiting the Middle East, echoed calls from President George W. Bush and the United Nations for Iraqis to pull together and not be pushed into sectarian strife by a bloodless but highly symbolic attack blamed on al Qaeda?s leader in Iraq, Abu Musab al-Zarqawi.

?The only people that want a civil war in Iraq are the terrorists like Zarqawi,? she told reporters. ?The Iraqi people are working under extremely difficult circumstances to bridge sectarian differences.?

The United Nations Security Council, rarely able to find a common voice on Iraq since its bitter divisions over the U.S. invasion in 2003, sounded a note of alarm in calling on Iraqis to rally behind a non-sectarian government.

?The members of the Security Council understand the anguish caused by the attacks but urge the people of Iraq to defy its perpetrators by showing restraint and unity,? it said.

Sistani, the Shi?ites? reclusive and ageing senior cleric, made a rare, if silent, television appearance that underlined the gravity of the crisis.

Since US forces toppled Saddam?s Sunni-dominated government, Sistani has helped hold in check anger many Shi?ites feel against al Qaeda and other Sunni militants as the Shi?ite majority tastes power after years of oppression.

Sunnis accuse police of running death squads against them and some powerful Shi?ites, buoyed by success in December?s election, have said only Sistani has prevented more violence.

Mussab AL-KHAIRALLA Alastair MACDONALD