The blast occurred outside the residential offices of Supreme Council for the Islamic Revolution of Iraq (SCIRI) leader Abd al-Aziz al-Hakim, who escaped injury.
Al-Hakim later called the attack an attempt to assassinate him. He blamed Sunni Muslim insurgents, but he said his party will maintain its path of nonviolence.
Al-Hakim is a leading candidate of the United Iraq Alliance in the general elections slated for 30 January. His alliance links major parties representing Shi'ites, the majority religious group in Iraq.
Meanwhile, Iraq's top Sunni party today withdrew from the elections, saying violence would make it too hard for people to vote in the Sunni north and west.
"Today the party took a very difficult decision, which was to withdraw from the elections because it is convinced that the
situation will not improve to allow conditions for credible elections within that time frame [30 January]," Iraqi Islamic Party Secretary-General Tariq al-Hashimi explained in announcing the move.
Another top official of the same party, Mohsan Abd al-Hamid, said that the Iraqi Islamic Party is not calling for others to join the boycott of the January polls.
(Reuters/AP/AFP)[For more RFE/RL news and analysis of events in Iraq, see our dedicated The New Iraq webpage.]