At least 27 people have been killed in a suicide bomb attack on a police headquarters in the Iraqi city of Baquba, north of Baghdad, police say.

At least 20 people were hurt. Most victims were police recruits.

Correspondents say the attack bears the hallmarks of militant al-Qaeda in Iraq, who often targets recruits.

Baquba is the capital of Diyala province, where some local tribes have recently joined US and Iraqi forces to fight the group.

On Sunday, nine tribal leaders from Diyala province were kidnapped while returning from Baghdad.

Violence levels falling

Police said the bomber arrived at the scene of the attack on a bicycle dressed in civilian clothes concealing a suicide belt.

He blew himself up as recruits waited to begin the day's training session.

Baquba's chief of police was killed in a suicide attack last month.

The September attack happened in a mosque compound during reconciliation talks between Sunni and Shia groups.

But the BBC's Jim Muir in Baghdad says levels of violence have generally been falling since a US troop surge began in February.

The US was set to hand over the mainly Shia central province of Karbala to Iraqi control on Monday.

It will be the eighth of 18 provinces to be transferred to local control since the US-led invasion in 2003.

PHOTO CAPTION

Map showing the Iraqi city of Baquba

 BBC