More than 30 people, including 24 police officers, have died in the second consecutive day of carnage in Iraq today as relatives of the 180 victims of yesterday's bloodshed buried their dead.

A car packed with explosives rammed into a patrol convoy passing a bus stop in the southern Baghdad district of Dura at 8am (0500 BST) bringing renewed violence to the capital. Fifteen high-ranking police commandos died and a dozen more were injured.

Four hours later, two suicide bombers struck within a minute of each other, the twin booms of their explosions shaking the south of the capital, killing at least seven special forces police and injuring another 10.

Three civilians died when a roadside bomb struck a Ministry of Industry bus in the east of the city.

Shortly after yesterday's wave of explosions and shootings, a group linked to Abu Musab al-Zarqawi, calling itself al-Qaeda in Iraq, claimed responsibility on an Islamist website and urged all Sunni Muslims to "wake up from your slumber" and join the fight.

The group claimed that the attacks were revenge for a successful Iraqi and US joint military offensive against the rebel stronghold of Tal Afar, a staging post on the Syrian border used by foreign recruits, five days earlier.

The Times has learned that al-Zarqawi, considered to be Osama bin Laden's lieutenant in Iraq, has united insurgent groups in Baghdad to target the Shia community with the aim of bringing civil war to Iraq as it prepares for a referendum on its constitution next month.

The bloodshed continued beyond the confines of the capital this morning. Two police officers were killed and four wounded in a roadside bomb attack in the northern Iraqi oil city of Kirkurk.

Three Shia pilgrims heading to the southern city of Kerbala for a religious event were killed by gunmen in northern Baghdad. Six bodies riddled with bullets have also been found in the Shula and New Baghdad districts.

In an audio tape published on the internet whose authenticity has not been verified, al-Zarqawi, a Jordanian-born Islamist who has a $25 million price on his head, demanded that Iraq’s other religious groups disavow the government of Prime Minister Ibrahim Jaafari.

"If proven that any of [Iraq's] national guards, police or army are agents of the Crusaders, they will be killed and his house will be demolished or burnt - after evacuating all women and children - as a punishment," the speaker said.

"There will be all-out war against Shiites everywhere. Beware, there will be no mercy."

Mr Jaafari said in a statement issued from New York, where he was attending the United Nation's 60th anniversary summit, that he was determined "to pursue the war against terrorism and remove it from all corners of the country". The threat is being taken seriously by American and Iraqi officials.

An intelligence summary, citing the conglomeration of insurgent groups under the al-Qaeda banner to be the result of rebel turf wars, money, weaponry and fear, concluded that of the estimated 16,000 Sunni Muslim insurgents, 6,700 were Islamic fundamentalists who were now supplemented by a possible further 4,000 members after an amalgamation with Jaysh Muhammad, previously an insurgent group loyal to the former Baathist

Al-Zarqawi’s rise to supremacy will cast a long shadow in the run up to the October 15 referendum on Iraq’s new constitution and general elections due in December.

His organisation is believed already to have gained dominance of smaller resistance groups in Ramadi, the capital of Anbar province in western Iraq and a centre of gravity for the Sunni insurgency.

Coalition intelligence sources said that a culmination of signal, image and human intelligence had alerted the coalition to a huge al-Qaeda attack planned for Baghdad in August, which had been aborted at the last minute.

They said the yesterday’s attack was likely a rescheduling of the original operation, and broadcast for propaganda purposes as retaliation for recent government successes in Tal Afar, northern Iraq.

In Tal Afar itself yesterday, where some 10,000 American and Iraqi troops have been engaged in an offensive to recapture the ethnically divided town from Sunni insurgents, commanders spoke of the "horrible" abuses they had uncovered. The details were prophetic reminder of what al-Qaeda’s supremacy may bode.

"The enemy here did just the most horrible things you can imagine, in one case murdering a child, placing a booby trap within the child’s body and waiting for the parent to come recover the body of their child and exploding it to kill the parents," said Colonel H R McMaster, a senior American commander.

Yesterday commanders said they were in full control of the town after the insurgents melted away, but their victory appears quickly overshadowed by al-Zarqawi’s subsequent gore-splattered stamps acoss the very centre of Baghdad.

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