BAGHDAD - A female suicide bomber wearing a vest packed with explosives killed 16 people on Friday in an attack northeast of Baghdad on former Sunni Arab insurgents who have joined with security forces to fight al Qaeda, police said.
Another 27 people were wounded in the blast in the town of Muqdadiya, 90 km northeast of Baghdad, in volatile Diyala, a religiously and ethnically mixed province which has become one of the most dangerous areas of Iraq.
Women and children were among the wounded, police said.
A "surge" of 30,000 extra U.S. troops and the growing use of neighbourhood security patrols, organised by mainly Sunni Arab tribal leaders, has helped reduce violence in Iraq to its lowest levels in almost two years.
The security crackdown has squeezed Sunni Islamist al Qaeda out of their former stronghold in western Anbar, where the neighbourhood units sprang up last year, into other areas north of Baghdad like Diyala.
Police said Friday's attack targeted a building used by members of the 1920 Revolutionary Brigades, a Sunni Arab insurgency group. A number of its members have begun working alongside security forces against al Qaeda.
While overall attacks have fallen 55 percent in Iraq since the "surge" was fully deployed in mid-June, General David Petraeus, commander of U.S. forces in Iraq, warned on Thursday that al Qaeda remained a dangerous foe that would seek to launch major assaults.
A militant group linked to al Qaeda in Iraq issued a threat on the Internet earlier this week vowing to launch a wave of car bomb attacks and strikes against Iraqi security forces.
U.S. commanders have identified Diyala and other areas of northern Iraq as the epicentre of the fight against al Qaeda.
Colonel Raymond Thomas, an assistant commander of the U.S. division responsible for northern Iraq, on Wednesday said more troops were being sought for Diyala.
Suicide bombings carried out by women are rare in Iraq.
A similar attack by a female suicide bomber wounded seven U.S. soldiers and five Iraqi civilians on November 27 in Baquba, the capital of Diyala.
