Updated

About 30 gunmen ambushed a car Sunday in central Baghdad (search) carrying employees of the Iraqi organization running next month's elections, killing three of the workers while two escaped unhurt, an official from the election body said.

Adel al-Lami, a member of the Independent Electoral Commission of Iraq, said the early morning attack took place in downtown Baghdad's Haifa Street (search ), the scene of repeated clashes between security forces and insurgents.

Al-Lami said about 30 militants ambushed a car carrying five employees working for the commission's Baghdad office, hurling hand grenades at the vehicle and firing at it with machine-guns.

Three employees, including a security guard, were killed in the brazen ambush, while two escaped unhurt.

"They tried to drag them out of the car," he said of the militants, who eyewitnesses said later set fire to the vehicle and wandered the street openly brandishing their weapons.

Meanwhile, a homicide car bomber detonated his vehicle outside Karbala's main bus station Sunday, killing 13 people and wounding 30, a hospital official said.

Police spokesman Rahman Mashawi said the Karbala blast happened at 1:30 p.m. outside an entrance to the crowded station in downtown Karbala, a predominantly Shiite city 50 miles south of Baghdad.

"This is a terrorist attack carried out by terrorist groups in order to destabilize the security in the city," Mashawi said.

Five cars erupted in flames after the blast, and about 10 passenger minibuses were destroyed. Police cordoned off the chaotic scene, as firefighters tried to put out the fires.

Ambulances ferried the wounded to the nearby al-Hussein Hospital, where medical workers struggled to treat people suffering from severe lacerations and burns.

Ali al-Ardawi, assistant for the hospital's director, said 13 people were killed in the attack and 30 injured.

The bus station is about 200 yards from the compound of the shrine of Imam Hussein, one of Shiite Islam's most beloved saints, which was the scene of a March 2 homicide bombing that killed 85 people and wounded 100.

Also Sunday, witnesses said a car bomb exploded in Najaf near the revered Imam Ali shrine compound on Sunday and that and ambulances are heading to the area. There was no immediate word on casualties.

A black plume of smoke rose over the city, 100 miles south of Baghdad, after the blast. Witnesses said the explosion went off 400 yards from the shrine of Imam Ali in Najaf, the holiest Shiite site in Iraq.

The blast happened at about 3:30 p.m., two hours after the Karbala explosion.