The U.S. military says it has captured a key aide to radical Shi'ite cleric Moqtada al-Sadr during a series of overnight raids in the southern Iraq city of Najaf.

American Brigadier General Mark Kimmitt told reporters in Baghdad Wednesday that Riyad al-Nouri, a relative of Moqtada al-Sadr, will be handed over to Iraqi authorities to stand trial for his alleged involvement in the killing last year of a Shi'ite cleric Abdul Majid al-Khoei.

Moqtada al-Sadr is also wanted in connection with that murder.

General Kimmitt also said a "very large number" of militiamen were killed in overnight clashes with U.S. forces in Najaf, but he did not give a precise figure.

In Baghdad, three Iraqis were killed and nine wounded by a roadside bomb early Wednesday.

And a Russian energy company Interenergoservice says it is evacuating all its workers in Iraq, after two employees were killed and five wounded in an ambush on their bus in the Baghdad area. Two Iraqis were also killed.

Earlier this month, the company evacuated 109 workers after one of its employees was killed in an attack south of Baghdad.