Two suicide bombers on Wednesday blew themselves up inside a police commando base in the city of Mosul, the capital of Iraq's northern province of Nineveh, killing the commander of the base and three policemen, a provincial police source said.

The attack took place at about 6:30 a.m. (0330 GMT) when two suicide bombers detonated their explosive vests near the room of Lieutenant Colonel Shamil Ahmed, the commander of the 1st battalion of the police commando which is stationing in Bab Sinjar area in western Mosul, some 400 km north of Baghdad, the source told Xinhua on condition of anonymity.

A third suicide bomber was shot dead by the police before he entered the base, the source said.

The body of Ahmed is still under debris, the source said, adding that three more police commando members were also killed by the blasts and many others were wounded.

The toll could rise as powerful blasts destroyed parts of the building and, apparently, many others are buried under the demolished walls, it added.

Nineveh province has long been a stronghold for insurgent groups, including al-Qaida militants. The province has been the scene of major security crackdowns by the U.S. troops and Iraqi security forces to uproot the insurgency which erupted shortly after the U.S.-led invasion in 2003.