A man cries during an anti-US protest march in Baghdad. (AFP)

Baghdad, March 3 (Reuters): Sunni and Shia leaders stood side by side in Baghdad today to urge Iraqis to avoid a civil war after suicide attacks on a holy day killed scores of Shia worshippers.

Thousands of Shias converged on their holiest Baghdad shrine to mourn the more than 70 of their brethren killed in a bombing yesterday that occurred at nearly the same time as an attack killed dozens of others in the city Karbala.

Hundreds of Shias waved black flags of mourning and backed their clerics’ plea for unity, chanting: “We are brothers, Sunnis and Shias, and we will not sell our country to foreigners.”

Witnesses recounted grisly tales of human flesh flying through the air after the blasts. Many watched as cleaners swept the remains of darkened dried blood stains.

Some turned their anger on the US, which has occupied Iraq since toppling Saddam Hussein 11 months ago. Some assailed Washington’s chief West Asia ally, Israel. Shias, who make up 60 per cent of Iraq’s people, were suppressed for decades under Saddam, a Sunni.

“We are facing critical hours and dark days... so open your eyes against the plots of America and Israel to sow dissension,” said Moayad Naimi, imam of the main Sunni shrine of Abu Hanifa in Aadhimiya across the Tigris river. “Iraq will only rise with both Sunnis and Shias,” he said, adding his followers had rushed to donate blood for the Shia victims. Clerics told Iraqis not to be provoked into civil war.

“If the two sides fight it’s the Americans who benefit to find an excuse to stay in Iraq,” said Sheikh Raed al-Kazemi, a Shia.

There was confusion over the death toll from the attacks. “The number of martyrs from the two cities as of this afternoon is 271,” governing council president Mohammed Bahr al-Uloum said in Baghdad. But health minister Khudier Abbass said the confirmed toll was 98 in Karbala and 71 in Baghdad, adding that 12 bags of human remains had yet to be identified.

Huge crowds of mourners marched through the holy city of Karbala chanting: “God is Greatest” and bearing flower-laden coffins aloft through streets packed with Shias. Thousands more, joined by Sunnis, converged on Baghdad’s most sacred Shia mosque to urge national unity and reject sectarian strife.

Many turned their anger instead on the United States -- accused by many Shi'ites, including their spiritual leader Ayatollah Ali al-Sistani, of not doing enough to make Iraq safe.

”Yes, yes to Islam. No, no to the infidels,” they chanted.

Supporters of radical Shi'ite cleric Moqtada al-Sadr, an outspoken opponent of the U.S.-led occupation, flocked to the bombed Kadhimiya mosque to vent anti-American feelings.

”Yes, yes to Islam. No, no to the infidels. We will defeat America,” they chanted near the gold-domed mosque.

Some blamed Wahabis, followers of an austere sect of Sunni Islam whom they said reviled Shi'ites as perceived heretics.

”Those who sanction the killing of Muslims have no faith. They cannot be true Muslims,” said Rida Dabagh, a weeping mourner.

Some Shi'ites said they had been restrained from violent revenge by their clergy's call for calm.

”If only our clergy would give us the signal we would wipe out the Sunnis from Iraq,” said an angry Mutaz al-Shamri, a traditional garments trader near the shrine.