U.S. forces said on Sunday they had caught two prominent al Qaeda leaders, including one they blamed for the kidnapping of an American journalist.

They said they had captured Ali Rash Nasir Jiyad al-Shammari, known as Abu Tiba, on August 17 and Salim Abdallah Ashur al-Shujayri, known as Abu Uthman, on August 11.

Abu Tiba was the Sunni militant group's senior advisor in the Iraqi capital, while Abu Uthman was its "emir," or leader, for the capital's eastern Rusafa district.

Abu Tiba was in charge of al Qaeda during its most active period in early 2007, they said in a statement.

Abu Uthman was believed to be the planner directly behind the kidnapping of U.S. journalist Jill Carroll, a reporter for the Christian Science Monitor who was held for nearly three months after being abducted in 2006.

His associates were also involved in the kidnappings of British/Iraqi aid worker Margaret Hassan, who was slain by her captors in 2004, and of a group of Christian peace activists, the statement said.

"The capture of Abu Tiba and Abu Uthman eliminates two of the few remaining experienced leaders in the AQI (al Qaeda in Iraq) network," U.S. military spokesman Rear Admiral Patrick Driscoll said.

U.S. forces say al Qaeda militants have been driven out of many areas over the past year-and-a-half since many Sunni Arab tribes turned against them, but the militants still retain the capability to stage suicide bombings and other big attacks.