Baghdad ? A car bomb exploded Thursday at a bus station in a mostly Shiite west Baghdad neighborhood, killing 22 people. Officials received word that 20 decapitated bodies had been found near the capital but were unable to confirm the report because of fighting.

In addition to the dead, more than 50 people were wounded in the rush-hour blast in the Baiyaa neighborhood, police said on condition of anonymity because they were not authorized to release the information.

A huge fireball incinerated about 40 minibuses as people were lining up to catch rides to work, police and survivors said.

Associated Press Television News video showed the area littered with smoldering vehicle parts and charred bodies – their clothing in tatters. Bystanders, some weeping, gingerly loaded human remains into ambulances and pickup trucks.

No group claimed responsibility for the blast, but suspicion fell on Sunni militants.

U.S. and Iraqi commanders have launched operations in towns and villages around the capital in hopes of stopping the flow of car bombs into Baghdad, where thousands of American troops have been deployed since February to try to restore order.

One American soldier was killed Thursday and another was wounded by a roadside bombing during a combat patrol in eastern Baghdad, the U.S. military said.

To the south, two policemen from separate commands said villagers had reported finding 20 beheaded bodies near the Sunni Muslim village of Um al-Abeed. The village is near the city of Salman Pak, 15 miles southeast of the capital.

Villagers said the victims were all men aged 20 to 40 and that their hands and legs had been bound, the two officers said on condition of anonymity because they were not authorized to release the information.

Another police officer in eastern Baghdad said officials had heard the report and tried to send a force to the area to confirm it. The visit was called off because the area was too dangerous because of clashes between police commandos and extremists.

An official in Prime Minister Nouri al-Maliki’s office said he had seen no such report. He also spoke on condition of anonymity because he was not supposed to talk to media.

Maj. Alayne Conway, a U.S. military spokeswoman, said U.S. aircraft spotted what appeared to be five bodies on the east side of the Tigris River north of Salman Pak. American ground troops were sent to investigate but could not find the bodies.

Fears of more sectarian violence rose Thursday when radical Shiite cleric Muqtada al-Sadr vowed to go ahead with a planned march July 5 to the devastated Askariya shrine in Samarra.

Al-Sadr, head of the notorious Mahdi Army militia, said the goal was to unite Sunnis and Shiites against the Americans and Sunni extremists responsible for attacks against civilians.

But the government and Sunni organizations have urged al-Sadr to cancel the march, fearing it will provoke attacks by Sunni insurgents and further enflame sectarian violence.