Gunmen in Baghdad have attacked Shi'ite pilgrims on their way home after celebrating an important religious holiday.

In the apparent case of sectarian violence, Iraqi police say at least two Shi'ites died and dozens were wounded when gunmen opened fire Wednesday on a bus and a truck carrying the pilgrims. They had just arrived in western Baghdad after attending the Shi'ite mourning ritual of Arbayeen in the holy city of Karbala.

The gunmen ambushed police rushing to the scene, and two policemen died.

Earlier Wednesday, Iraqi police, with U.S. troops, captured at least 50 insurgents who had stormed a police station south of Baghdad, killing at least four policemen.

Separately, President Bush said it is important for Iraqis to begin taking the lead in the fight for their future.

In a speech in the U.S. state of West Virginia, Mr. Bush also said he will decide on U.S. troop levels in Iraq based on what U.S. military officers advise and not on "polls, focus groups or election-year politics."

In New York, CBS Television said an Iraqi cameraman,  Abdul Ameer Younis Hussein, detained for allegedly collaborating with insurgents, will go on trial within days. The cameraman was a freelancer working for the network. The Committee to Protect Journalists has called his treatment "alarming" because he has been held without charge for almost a year.

In other news, the U.S. military says coalition forces killed four al-Qaida terrorists and detained one during a raid on a top al-Qaida cell leader near the city of Samarra.