Baghdad (CNN) -- Violent overnight attacks in Iraq killed nearly two dozen people Sunday.
A suicide bomber detonated a car rigged with explosives at the main entrance of the police academy in eastern Baghdad, killing at least 15 people as recruits were leaving, Iraqi police officials said.
The attack, which occurred on the traditional start of the work week in the Arab world, wounded at least 21 others, police officials said.
The officials spoke on condition of anonymity because they were not authorized to release details to the media.
Officials had first said the suicide bomber detonated an explosives vest, then later said it was a suicide car bombing. The attacker had his car parked close to the building and waited for a group of recruits to walk out before he drove up and detonated the device.
While nobody claimed responsibility, officials said they believed al Qaeda in Iraq was behind the attack.
The Baghdad police academy is the only one in the capital and is within the compound of the heavily guarded Interior Ministry, but has a separate entrance.
North of Baghdad, in Diyala province, seven others were killed in two attacks. In the first incident, four people were gunned down at a house late Saturday night. Three others were shot dead by gunmen who opened fire at a checkpoint just south of Baquba, the provincial capital.
Among the victims were members of awakening councils -- groups mainly made up of Sunni Arab fighters who turned against al Qaeda. The U.S.-backed movement is credited for helping reduce violence, though council members have become targets for militants.
The latest attacks come as Iraq remains mired in a political crisis split along sectarian lines, which has raised fears about a return to the levels of violence that nearly tore the country apart in 2005 and 2006.
The bloodshed has also generated uncertainty about the ability of Iraqi security forces to ensure order, particularly after the United States withdrew troops at the end of 2011, as well as fear about the future.