Abdul Aziz al-Hakim, head of the Supreme Council for the Islamic Revolution in Iraq — the country's most powerful Shiite political group — was in his residence in Baghdad's Jadiriyah district when the attack occurred, said his spokesman, Haitham al-Husseini.
The blast, which shook the district and sent a cloud of smoke high above the area, killed 15 people and injured at least 50, said police Capt. Ahmed Ismail. Thirty-two cars on the street and near the gates were destroyed or damaged.
"It was a suicide attack near the gate leading to the office," al-Husseini said. "Several of the guards were killed and wounded."
In other developments:
Al-Hakim, the Shiite leader who escaped injury, heads the candidate list of the 228-member United Iraqi Alliance coalition, which is expected to dominate Iraq's new constitutional assembly following the first free elections on Jan. 30. The coalition is supported by Iraq's top Shiite cleric, Grand Ayatollah Ali al-Sistani.
Al-Hakim's son, Ammar, accused Saddam Hussein's followers of being behind the suicide attack.
"They are the remains of the dead regime and their allies who carried out similar criminal acts in the past," he said, adding that many of the blast victims were innocent civilians who happened to be on the street when the explosion occurred.
The residence, where al-Hakim has his home and offices, was previously the house of Tariq Aziz, a jailed former senior aide to Saddam Hussein who has been in prison since April last year.
Political and religious leaders of the Shiite community, who strongly back the holding of next month's vote, have been repeatedly targeted by the mainly Sunni Muslim insurgents since Saddam's ouster.
The Shiites, who make up about 60 percent of Iraq's 26 million people, have traditionally been dominated by the Sunni minority, which accounts for about a fifth of the population. Their leaders are eager to translate that numerical superiority into political power after next month's ballot — the first free elections since the overthrow of the monarchy 45 years ago.
In August 2003, a suicide bomber killed Ayatollah Mohammed Baqir al-Hakim, elder brother of Abdul Aziz and former leader of the Supreme Council for the Islamic Revolution in Iraq.
Like his late brother, Abdul Aziz Al-Hakim is a Shiite cleric who opposed Saddam Hussein from exile in Iran before returning to Iraq after last year's U.S.-led invasion.
The violence came a day after the Iraqi militant group Ansar al-Sunnah Army posted a video on the Internet purportedly showing footage from last week's suicide attack at a U.S. base in Mosul. The group claimed that the bomber slipped into the base through a hole in the fence during a guard change.
The footage showed a black-garbed gunman wearing an explosives belt around his body — apparently the suicide bomber, identified in the tape as Abu Omar al-Mosuli — bidding farewell to his comrades. The video gives no further details about the bomber beyond his name.
The Ansar al-Sunnah Army had earlier said it would release a video of last Tuesday's attack, which killed 22 people, including 18 U.S. service members and civilian contractors.
The bombing — the deadliest attack on a U.S. base in Iraq — has prompted a U.S. military investigation into how the bomber got onto the heavily guarded site and how security at bases can be improved.
In the first section of the video — with a time signature of Dec. 20, a day before the attack — three gunmen wearing black masks and clothes and holding automatic rifles are shown sitting in front of a black banner with the group's name on it. One of them, apparently al-Mosuli, sits on the left, wearing an explosives belt.
The gunman in the center reads a statement describes how the attack will be carried out. The authenticity of the video could not be independently verified.
The two men then embrace the one wearing the explosives belt.
An image then shows a map of the base, as one of the gunmen points out locations using a military knife. One location is marked "the dining hall" in Arabic.
A later outdoor video image — shot on Tuesday, when the attack occurred — shows a fireball rising from the distance with the accompanying sound of the explosion. A final image — shot from a vehicle driving past the base — shows the torn white tent that served as the base mess hall.