More than 130 people, including dozens who joined a demonstration against sectarian violence, were killed and 168 mosques attacked in violence across Iraq on Thursday, despite calls for calm from leaders fearful of civil war.

A day after a suspected Al-Qaeda bomb destroyed a major Shiite shrine, Sunni political leaders pulled out of talks on forming a national unity government, accusing the Shiites, including Grand Ayatollah Ali Sistani, of fomenting attacks on Sunni mosques. But President Jalal Talabani pressed ahead despite the Sunni boycott with a meeting that he had called to avert a descent towards a civil war.

Police and military sources tallied more than 130 deaths, mostly Sunnis, around Baghdad and Basra in the 24 hours since the bloodless but highly symbolic bombing of the Shiite Golden Mosque in Samarra, also know as the Imam Ali al-Hadi mausoleum. Dozens of Sunni mosques have been attacked and several burnt to the ground.

The main Sunni religious authority, the Committee of Muslim Scholars, said 168 Sunni mosques had been attacked, 10 imams killed and 15 abducted since the shrine attack. The Interior Ministry said it could only confirm figures for Baghdad, where it had reports of 19 mosques attacked, one cleric killed and one abducted.

In the bloodiest single incident, officials said 47 people who had taken part in a joint Sunni and Shiite demonstration against the Samarra bombing were hauled from vehicles and killed.

They were all dumped in a ditch beside the road, said Dhary Thoaban, deputy chairman of the Diyala regional council.

The Committee blamed the violence on Sistani, and other Shiite religious leaders who called for demonstrations against the shrine attack. Sistani had also urged restraint

"They are all fully aware that the Iraqi borders are open, and the streets are penetrated with those who want to create strife among Iraqis," Abdel-Salam al-Qubaisi said at a news briefing.

He said U.S. Ambassador Zalmay Khalilzad may also have enflamed the situation when he warned this week that the United States would not continue to support institutions run by sectarian groups with links to armed militias.

"Without doubt, these statements mobilized all the Shiites," Qubaisi said.

Radical Shiite cleric Moqtada al-Sadr accused the Iraqi government and U.S. forces of failing to protect the shrine, and ordered his militia to defend Shiite holy sites and Sunni mosques across Iraq.

Thousands of demonstrators carrying Shiite flags and banners marched through parts of Baghdad, Karbala, Kut, Tal Afar and the Shiite holy city of Najaf in protest against the shrine attack.

An Internet statement from the Mujahideen Council, which includes Al-Qaeda in Iraq, blamed Shiite leaders for blowing up the shrine to justify attacks and vowed a "shocking response."

In other attacks, a bomb blasted an Iraqi army foot patrol in a market in the religiously divided city of Baqouba, killing 16 people.

The Interior Ministry said all police and army leave was cancelled and curfews were extended as the country locks down for three days of national mourning.

The sectarian tensions occurred at a critical time for Iraq, as politicians struggle to form a new government two months after elections for the first full-term parliament.

The Iraqi Accordance Front, which won most of the minority Sunni vote in December's parliamentary elections, said it would need an apology from the Shiites before it would consider rejoining talks on a national unity coalition.

"We are suspending our participation in negotiations on the government with the Shiite Alliance," Tariq al-Hashemi, a senior official of the Iraqi Accordance Front, told reporters. "It is illogical to negotiate with parties that are trying to damage the political process," he said. The Front also demanded a pledge there would be no repeat of the violence.

Leaders attending the meeting called by Talabani agreed the best way to respond to the attack is to form a unity government "whose top job should be getting the security situation under control and fighting terrorism," the president told reporters.

"If the fire of internal strife breaks out, God forbid, it will harm everyone," he said.

Mahmoud Othman, a member of the Kurdish delegation, said "everyone" at the meeting spoke of the risk of civil war and expressed concern that Friday prayers, when tensions run high, could trigger a new outburst of violence.

It was not clear if broader government talks would now go ahead without the presence of the Accordance Front, which includes the Iraqi Islamic Party.

U.S. President George W. Bush condemned the attack on the Samarra shrine - blamed on Al-Qaeda's leader in Iraq Abu Musab al-Zarqawi - as an "evil act" and appealed for restraint.

"I appreciate very much the leaders from all aspects of Iraqi society that have stood up and urged for there to be calm," Bush told reporters.

The United Nations Security Council sounded a note of alarm in calling on Iraqis to rally behind a non-sectarian government.