BAGHDAD - When police came looking for a 19-year-old woman who they believed had been recruited by al-Qaeda to be a suicide bomber in a town north of Baghdad, they found that she was already dead - slain by her father, who told police he strangled her out of shame and cut her throat.

The killing of Shahlaa al-Anbaky, reported by police Friday, appeared to stem from a melding of two motives - partly to defend the family honor, partly to prevent her from joining the extremists. How much each weighed in her father's mind remained unclear.

Al-Qaeda has been recruiting women for suicide attacks because they can pass police checkpoints more easily than men, and can conceal explosives under an abaya, a loose, black cloak that conservative Muslim women wear. Suicide bombers have been al-Qaeda's most lethal weapon in Iraq, killing hundreds of civilians and Iraqi security forces.

The slaying took place in the town of Mandali, about 60 miles northeast of Baghdad in Diyala province. A few years ago, Diyala was one of Iraq's deadliest regions, torn by attacks by al-Qaeda and Sunni insurgents and vicious sectarian killings between Sunnis and Shiites.

Since Sunni tribal militias turned against al-Qaeda in 2005, the province has become much safer, but al-Qaeda still carries out deadly attacks there.

Authorities were still trying to put together a full picture of the killing.

A Diyala police spokesman, Maj. Ghalib al-Karkhi, said security forces had information that the young woman had ties to al-Qaeda, and on Thursday they raided the home of her father, Najim al-Anbaky. Under questioning, he told police he had killed his daughter a month ago because he found out she intended to blow herself up in a suicide attack for al-Qaeda.

The father, described by authorities as a small-time trader of chickens and sheep, led police to her grave in the backyard. The young woman had been strangled and her throat cut, Karkhi said.

The father was in custody, though no charges had been filed. Other family members could not be reached for comment.

Terrorists have long recruited Iraqi women to carry out suicide attacks. As security has tightened across the country, women can get past checkpoints, because there are rarely enough female police officers to inspect every woman passing by.