BAGHDAD - U.S. forces said that they waged successful battles against both Sunni and Shiite extremists, and announced yesterday that they had seized two men possibly linked to the capture of three American soldiers earlier this year.

The battles north and south of Baghdad came as the military was seeking to take advantage of the improving security situation in Iraq to carry out targeted operations against extremist groups and the foreign-led al-Qaeda in Iraq.

In recent weeks, the Americans have been fighting al-Qaeda extremists in the area around Muqdadiyah, about 60 miles north of the capital. The battle against insurgent groups has steadily moved away from Anbar province and Baghdad, and is now focused on the fringes of Diyala province.

In another operation targeting a Shiite extremist group southeast of Baghdad, U.S. military forces killed 11 militants yesterday. They were reportedly members of an extremist group that had broken away from Shiite cleric Muqtada al-Sadr's Mahdi Army.

Sadr has declared a cease-fire, and has said that any Mahdi Army members who do not abide by his freeze will no longer be considered members of the powerful militia.

The battle against the Shiite extremists took place in the early-morning hours in Kut, 100 miles southeast of Baghdad, a local police officer said on condition of anonymity because he was not authorized to speak to the news media.

The officer said eight militia members were killed; the U.S. military said in an e-mail to the Associated Press that it killed an estimated 11 fighters. The reason for the discrepancy was not immediately clear.

In a later statement, the U.S. military said the operation was targeting a suspect who was "reportedly responsible for attacks against Coalition forces."

The military also said it seized two suspects linked to the capture of three American soldiers taken during a May ambush near Youssifiyah, 12 miles south of Baghdad. The suspects were captured Monday and Tuesday in Ramadi, the capital of Anbar province.

The military said one of the suspects was thought to have facilitated the kidnapping and to have used his house to hide the soldiers. A weapon belonging to one of the U.S. soldiers was found at the residence of the other suspect.