A suicide attacker blew up a bomb-packed car at a Shiite religious foundation's headquarters in Baghdad on Monday, killing at least 22 people in the capital's deadliest blast in more than four months.

The attack comes amid a dispute between Iraq's Shiite and Sunni endowments, which manage the country's religious landmarks, over a shrine north of Baghdad, and a protracted political standoff that has raised sectarian tensions in a country racked by brutal communal bloodshed from 2006 to 2008.

Monday's attack struck at 11:00 am (0800 GMT) outside the Shiite endowment in Baab al-Muadham, central Baghdad, and left at least 22 people dead and more than 65 wounded, two medical officials said.

The bombing completely destroyed the endowment headquarters, its deputy chief, Sami al-Massudi, told AFP.

"We do not accuse anyone, but we call on the Iraqi people and especially on the sons of our religion to bury the strife because there is a plan to launch a civil war between the people, and between the Iraqi sects," Massudi said.

He said the Shiite endowment had received threats in recent days as a result of the dispute over the Al-Askari shrine, a Shiite Muslim site in the mostly Sunni city of Samarra, north of Baghdad.

The iconic gold-domed shrine was hit by a brutal Al-Qaeda suicide attack in February 2006 that ignited the country's bloody confessional violence.

Massudi and his aides had produced documents in recent days that attributed the management of the shrine to the Shiite religious endowment, sparking tensions with its Sunni counterpart.

"The issue of the Al-Askari shrine is a legal and constitutional issue, and it is our right, because it is a Shiite shrine," Massudi said.

AFP journalists near the site of Monday's attack said security forces cordoned off the scene and barred anyone from approaching the area.

Several cars and nearby buildings were badly damaged by the explosion, and helicopters were hovering overhead. One man threw his spectacles to the ground and yelled: "They are all dead! They are all dead!"

The spike in attacks has coincided with a ratcheting up of months-long political tensions in which several political parties have called for Prime Minister Nuri al-Maliki to be unseated.

"Maliki and Allawi are fighting over the government, and we are the victims," said Mohammed, who owns a restaurant opposite the Shiite foundation headquarters, referring to Iyad Allawi, a rival of Maliki.

"Come and see the houses that were destroyed on the heads of children," he said, shirtless and covered in blood. "In my two hands, I carried children from under the rubble."

The latest violence comes less than a week after a spate of bombings in Baghdad left 17 dead on May 31, shattering a relative calm in the city.

Monday's death toll was the highest from a single attack in Baghdad since a suicide car bomb outside a hospital killed 31 people on January 27.

Violence in Iraq has declined dramatically since its peak in 2006 and 2007, but attacks remain common, especially in Baghdad. A total of 132 Iraqis were killed in violence in May, according to official figures.