BAGHDAD (Reuters):

Al-Qaeda is changing tactics in Iraq's volatile Diyala province, the commander of U.S. forces in north Iraq said on Saturday, shortly after a suicide car bomb killed eight people in a northern oil refining town.

Major-General Mark Hertling said al-Qaeda fighters driven out of other areas were targeting Diyala using suicide vests and attacking neighbourhood police units. But a spate of attacks there did not reflect a wider surge in violence, he said.

North of Diyala, police said at least eight people were killed in what a Reuters witness said was a suicide car bomb attack in the oil-refining city of Baiji in the latest bombing.

The U.S. military also said its soldiers had killed 12 suspected al Qaeda gunmen and detained 13 others in operations north and south of the capital.

Religiously and ethnically mixed Diyala has become one of the epicentres of violence in Iraq after Sunni Islamist al-Qaeda and other fighters were squeezed out of western Anbar province, Baghdad and other areas by security crackdowns this year.

Deaths

At least 61 people have been killed and 90 wounded over the past week in five major bombing and shooting attacks in the province, which spans the Tigris and Diyala Rivers and spreads east to the Iranian border.

"As far as an upsurge in attacks, we have not seen that," Hertling told Reuters in an email.

"What we have seen is some instances of different types of attacks," he said, referring to the use of suicide vests and "desperate" attacks against neighbourhood police units which the military calls "concerned local citizens".

On Friday, a woman wearing a vest packed with explosives killed 16 people in the Diyala town of Muqdadiya. The attack targeted former Sunni Islamist insurgents who had joined security forces to fight al-Qaeda, a rare attack by a female suicide bomber.

About 10 Iraqi troops were killed in another attack north of Muqdadiya later on Friday, security officials said.

Violence across Iraq has fallen by 55 per cent since an additional 30,000 U.S. troops became fully deployed in mid-June.