Charles W. Gill, Getty Images
Army Sgt. Warren Bryson provides security during a combined patrol with Iraqi police in Baghdad.

BAGHDAD (AP) — A car bomb killed at least seven children and 11 other people in a northern city, providing a reminder that militants still can cause casualties despite security improvements that led U.S. troops to return a southern province to Iraqi control Wednesday.

Ninety people also were injured in the blast at a popular outdoor market in Tal Afar, said a police official, who insisted on anonymity because he was not authorized to speak to the media.

The city, a one-time stronghold of Sunni insurgents 260 miles northwest of Baghdad, was targeted in offensives by U.S. and Iraqi troops that prompted American leaders to describe it as a success story in the effort to stabilize Iraq. But sporadic attacks continue.

In Afghanistan, U.S. troops abandoned a remote eastern outpost where militants killed nine of their comrades this week, officials said Wednesday, in another sign of the struggle facing foreign and Afghan security forces strung out along the mountainous border.