Hakim, head of one of the country's main Shia political parties, the Supreme Council for the Islamic Revolution in Iraq (SCIRI), escaped with his life but a number of his guards were killed.

A giant fireball knocked down walls and shattered windows at Hakim's offices in the latest attack against the country's majority Shia community in the run-up to next month's crucial elections.

"Thirteen people were killed and 66 were injured and about 60 cars were destroyed," an interior ministry official said.

At least one woman was among the dead, hospital sources said.

A speeding explosives-packed car hurtled towards the gates of Hakim's spacious mansion in the southeastern Jadriyah district at 9:30 am (0630 GMT), said a spokesman for SCIRI.

"We had an attack against our offices here by a suicide bomber. It seems he was trying to get through the main gate, but his vehicle exploded," Haitham al-Husseini told this news agency.

Husseini blamed toppled dictator Saddam Hussein's old Baath party for the attack, saying: "It was elements of the old regime and other extremists trying to stop the political process in Iraq."

Around Hakim's office, the former home of Saddam's deputy prime minister Tareq Aziz, US military vehicles blocked the road and US soldiers stood behind razor wire barricades.

Residents recounted the early morning scene of carnage.

"A car was speeding down the wrong side of the street. The guards tried to stop him but they couldn't," said a neighbour, Rafed Adel.

Store owner Iyad Allawi added: "I heard a strong explosion and a fireball rose into the sky. There was smoke in front of their offices. We ran and I heard glass shattering. I saw several bodies being taken away in a pick up."

Hakim's followers, already grieving the deaths of more than 100 SCIRI members since their return to Iraq after the April 2003 fall of Saddam, were relieved to hear their political leader emerged unscathed.

"Thank God, Abdel Aziz Hakim and the other members of his family are safe and sound," said Hakim's son Mohsen Hakim in Tehran.

He said four or five security guards died, while a spokesman at Hakim's offices said three or four guards were killed and several others wounded.

Iraq's Shiites, who make up 60 percent of the country's 25 million population, are on the cusp of a huge victory in Iraq's crucial January 30 national polls.

After years of oppression under Saddam, Iraq's religious majority is expected to win the lion's share of seats in the nation's 275-member parliament that will be charged with writing the country's first post-Saddam constitution.

Hakim is also the top candidate on the Shiite coalition called the Unified Iraqi Alliance running in the landmark January elections.

The 228-man Shiite list is the early election favourite, due to its endorsement from Grand Ayatollah Ali al-Sistani, the most revered Shiite cleric in all of Iraq.

SCIRI's founder, Ayatollah Mohammed Baqr Hakim, the brother of Abdel Aziz, was assassinated in a car bombing that killed 83 people in the Iraqi Shiite shrine city of Najaf in August 2003.

Twin bombings against the Iraqi holy Shiite cities of Karbala and Najaf on December 19 killed a total of 66 people and wounded nearly 200.

Abdel Aziz Hakim lived in Iran since the early 1980s, where he headed SCIRI's former military wing, the Badr Organisation, before his return to Iraq in spring 2003.