Iraq's election chief started the clock Friday on the long-awaited formation of a new government, announcing final certified results for the country's Dec. 15 parliamentary polls.

A car bomb exploded outside a Sunni Muslim mosque in southwestern Baghdad, killing at least four Iraqis and wounding 21. Gunmen wearing Iraqi police uniforms kidnapped a Sunni Arab mosque preacher in Baghdad.

Intense negotiations are under way to form a national unity government that would see dominant Shiites and Kurds welcome Sunni Arabs into powerful positions.

Friday's announcement by Adil al-Lami, head of the Independent Electoral Commission of Iraq, confirmed initial results released last month. The certification means the new 275-seat parliament, the first post-Saddam Hussein assembly with a four-year mandate, must convene within two weeks.

Al-Lami said the dominant Shiite coalition, the United Iraqi Alliance, won 128 seats. The Kurdish Coalition of parties led by President Jalal Talabani and Kurdish leader Massoud Barzani were the other big winners, claiming 53 seats.

He said two Sunni Arab blocs, the Iraqi Accordance Front and the Iraqi Front for National Dialogue, received 44 and 11 seats respectively. Sunni Arabs now have three times more seats than in the outgoing parliament.

Sunni Arabs form the backbone of the raging insurgency, and bringing them into the government is seen as a way to reduce the violence.

Under Iraq's new constitution, Talabani not only must convene the new assembly, he must also name a new prime minister in the next 15 days. Parliament then has 30 days to elect a new national president.

If the Iraqis take the maximum time allowed for each step, it would be May before a government is in place. Vice President Adil Abdul-Mahdi, a Shiite widely mentioned as possible prime minister, has said he expected to finish the talks by mid-March.

But sectarian violence threatens the fragile U.S.-backed political negotiations. Armed Shiite Muslim and Sunni Arab militants have been targeting each other in a worsening campaign of killings and kidnappings.

Friday's car bomb was parked about 10 yards from the Iskan al-Shaabi mosque in the southern Dora neighborhood when it exploded after 1 p.m., shattering glass in the building and causing casualties inside and outside, said police Lt. Thaer Mahmoud.

Police forces cordoned off the scene and prevented journalists approaching the mosque, where worshippers were attending the main weekly Muslim prayer service.

Ahmed Hassan, 36, was praying inside the mosque at the time.

"Some worshippers were leaving and others were praying inside when the explosion blasted glass all over us and smoke filled the mosque," Hassan said. "Outside we were shocked to see so many wounded people and cars on fire."

Lt. Mohammed Khayoun said at least four people were killed and another 21 wounded, most of them mosque worshippers.

An Interior Ministry official, who declined to be identified because he was unauthorized to speak to the media, confirmed those numbers.

Earlier Friday, gunmen wearing Iraqi police uniforms seized a Sunni Arab mosque preacher from his home in Baghdad, police said.

Adel Khalil Dawoud, imam of the al-Nuaimi Sunni Muslim mosque in Baghdad, was taken after midnight in the downtown Karradah district, said Lt. Mohammed Khayoun.

Sunni Arabs have been long complaining about Shiite Muslim-backed Interior Ministry police forces and militias kidnapping and killing Sunnis, including religious leaders.