U.S. army Gen. David Petraeus gestures as he speaks during a press conference in Baghdad, 8 March 2007

The new U.S. commander in Iraq says military action alone will not end the violence in the war-torn country, noting that political talks also are critical.

General David Petraeus said Thursday those talks must include militant groups.

The general, in his first news conference since taking command last month, also said sectarian killings have fallen since a new security crackdown began in Baghdad and al-Anbar province.

He divided insurgents into three categories, al-Qaida in Iraq, sectarian militants and violent criminals, and said all are trying to derail the crackdown by inciting more violence between Sunni Arabs and Shi'ites.

In violence Thursday, the U.S. military says 28 people were killed in a suicide bombing in the Iraqi city of Dor Mandali. A separate statement says coalition forces killed seven terrorists and captured six others while targeting al-Qaida in Iraq.

More than 150 people have been killed in recent days in attacks against Shi'ite pilgrims traveling to Karbala, south of Baghdad, for religious observances.