A 13-year-old Iraqi girl wearing a vest packed with explosives turned herself in rather than go through with a suicide bombing in a violence-torn city north of Baghdad, the US military said.

A statement said the girl surrendered to police on Sunday in Baquba, capital of Iraq's restive Diyala province, where Sunni Arab al Qaeda militants are waging war on US and Iraqi forces.

She was still wearing the vest, which police had to remove before detaining her.

"Reports are that she approached the IPs (Iraqi police) saying she had the vest on and didn't want to go through with it," US military spokesman Lieutenant Commander David Russell told Reuters on Monday. "If she was forced to put on the vest or if she did it voluntarily, that is still being reviewed."

Suicide bomb attacks by women and girls have become increasingly common in Iraq this year. US forces say al Qaeda Sunni Arab militants favour female bombers because they can escape detection by police reluctant to search women.

Female suicide bombers attacked Shi'ite pilgrims during two annual rites in recent weeks, killing dozens. Many attacks by female suicide bombers have taken place in Diyala.

"The surrender of the suicide bomber indicates that the Iraqis are continuing to reject al-Qaeda and its practices," US military spokesman for north Iraq Major Jon Pendell said.

Iraq has become far less dangerous over the past year, but militants are still able to carry out devastating bombings.

A male suicide bomber killed 25 people at a dinner banquet in western Baghdad's Sunni Arab Abu Ghraib district on Sunday.