Ten soldiers were killed and 29 other people injured when a suicide bomber blew up his booby-trapped car outside an Iraqi army battalion headquarters in the country's east today.
The explosion destroyed the building.
Diyala provincial council spokeswoman Samira al-Shibli said emergency workers were still frantically trying to rescue victims from beneath the rubble several hours later.
Diyala health directorate spokesman Faris al-Azawi said the bomber drove his car past a security gate and detonated his explosives right outside the headquarters of an army intelligence battalion in Kanan, east of the provincial capital of Baqouba, 35 miles (60km) north-east of Baghdad.
An army commander in Diyala described a horrific scene of the building collapsing on soldiers inside. He said the bomber drove his car up through a back gate and through a yard to get to the headquarters.
Mr Al-Azawi said 10 soldiers were killed and at least 29 other people were injured, including 14 soldiers.
Ms Al-Shibli said a second bomb was discovered nearby but defused by officials before it could explode. She said the first blast may have been from a bomb in a parked car.
A senior Iraqi intelligence official in Baghdad blamed the attack on al-Qa'ida and said authorities believe the same cell of insurgents may also be plotting a similar strike against security forces in the capital.
He said al-Qa'ida suspects being held in prison have tipped off authorities to the threat, and said insurgents have already planned a strike in Baghdad but need funding to carry it out.
In January, the Islamic State of Iraq, an al-Qa'ida front group, claimed responsibility for two bombings at security force headquarters in Baqouba which killed 10 people.
Also today, a local politician in the central Salahuddin province said one inmate was killed yesterday by jumping off the roof in a bid to escape from prison during a riot.
Provincial council member Abdullah Jabara said 22 people, including 15 guards, were injured in the melee which started after officials found holes in the jail's steel fence and discovered an escape plan by inmates linked to al-Qa'ida.
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