A car packed with explosives detonated Monday outside the Baghdad residence of the leader of Iraq's most powerful Shi'ite political group. Police say the apparent suicide attack left at least at least 13 people dead and dozens of others wounded.

Minutes after the explosion, Iraqi and U.S. forces sealed off a busy intersection in Baghdad's Jadiriyah district to make way for ambulances and medical personnel.

A cloud of thick smoke could be seen billowing from the home of Abdul Aziz al-Hakim, the head of the country's largest and most powerful Shi'ite political party, the Supreme Council for the Islamic Revolution in Iraq, also known as SCIRI.

SCIRI party officials say Mr. Hakim was home at the time of the blast, but escaped unhurt.

Casualties included several security guards and employees, who were in the reception area of the house when the bomb went off near the front gate. Eyewitnesses say some of the others hurt or killed in the explosion were motorists waiting in line at a nearby gas station.

Mr. Hakim's neighbor, Tariq al-Shaikhli, expressed frustration about the continuing violence, which U.S. and Iraqi officials say could even escalate in the run-up to Iraq's first free elections scheduled to take place on January 30.

"Who does this? Definitely people who are well-organized and trying to unbalance Iraqi society," said Mr. Shaikhli. "They don't want Iraq to be settled and looking forward to elections."

Adbul Aziz al-Hakim leads a religious party founded in Iran by exiled Iraqi Shi'ites to oppose the regime of former dictator, Saddam Hussein.

Mr. Hakim returned to Iraq last year, soon after U.S.-led forces toppled Saddam from power. The Shi'ite cleric took over as the head of SCIRI after his elder brother, Ayatollah Mohammed Baqir al-Hakim, was assassinated in last August's bombing of a major Shiite shrine in the southern city of Najaf.

Mr. Hakim now heads the candidate list of the 228-member United Iraqi Alliance coalition, a Shi'ite group which is expected to dominate the elections. The group is supported by Iraq's top Shiite cleric, Grand Ayatollah Ali al-Sistani.

Shi'ites make up about 60 percent of Iraq's 26 million people but suffered under the country's Sunni Muslim rulers for decades.

Shi'ite leaders view next month's ballot as an opportunity to turn their numerical superiority into political power. But that has led to concerns that a Shiite victory in the polls could alienate Sunni Arabs and create more social chaos.

Citing the on-going security problems in Iraq, some Sunni leaders have already called for a boycott of the election. On Monday, the largest Sunni Muslim political party that had planned to take part on January 30 pulled out of the race, urging the Iraqi Electoral Commission to delay the elections for at least six months.

The Iraqi Islamic Party says it feels the country is too insecure right now to hold elections and says more time is needed to ensure that all Shi'ites and Sunnis will participate in the voting process.