Tikrit, Iraq - Scores of gunmen took over a federal police headquarters in northern Iraq on Friday before driving a tanker laden with explosives into the building, killing many, a government official said.
The battalion commander and his assistant were among the dead but the total number of casualties was still impossible to ascertain because victims remained trapped beneath the building in the village of Injana, the official said.
The mayor of the nearby town of Sulaiman Pek, 160 km (100 miles) north of Baghdad, said security forces were still fighting the gunmen, who also seized control of another town in the area called Serha.
Militants occupied Sulaiman Pek last month and raised the black flag of the Sunni Islamic State in Iraq and the Levant (ISIL) over it.
Security officials said the tanker bombing might have targeted Brigadier General Raghib Ali in revenge for his role in driving the militants out of Sulaiman Pek.
ISIL, which is also active in neighbouring Syria, has regained momentum in Iraq over the past year and is one of a number of insurgent and tribal groups that stormed the cities of Ramadi and Falluja in the western province of Anbar in January.
In Ramadi, six people were killed when a suicide bomber blew himself up inside a mosque where a funeral was being held for an officer who died in a roadside bombing earlier this week, medical and security sources.
Meanwhile in Falluja, about 300 militants paraded through the main streets of Falluja late on Thursday, dressed in black and bearing ISIL's banner. They showed off military Humvees, armored vehicles and some weapons they said they had taken from soldiers during the fighting.
Residents of Falluja lined the road, welcoming them with with cries of “you are heroes!” and showering them with chocolates.
Shi'ite Prime Minister Nouri al-Maliki has declared war on Sunni militants, appealing for arms and international support to help quell an insurgency he paints as an extension of the civil war in Syria.
Maliki's critics say his own policies have marginalised the country's once-dominant Sunni minority and created the conditions for militants to thrive.