A suicide car bombing in the Iraqi city of Tikrit has killed at least 12 people, police say.
At least another 19 people were injured in the attack which struck the hometown of the former leader Saddam Hussein.
The attack targeted the entrance to a complex of palaces which formerly belonged to him and which currently houses security offices.
It comes three days after attacks on a Tikrit mosque and hospital killed at least 21 people.
Monday's attack was "a suicide car bomb that blew up at the main gate while a process of handing over checkpoints from the police to the army was taking place", Hassan Abdulla, media adviser to the head of the local provincial council, told Reuters news agency.
Mr Abdulla said those killed included several military officers, among them a colonel who was the head of military intelligence in Tikrit.
There was reported to be widespread damage to buildings in the complex, which has been likened to a local version of Baghdad's heavily fortified Green Zone of government and administrative buildings.
In other violence, at least four people have been killed in attacks in the capital Baghdad.
They died in two attacks on security checkpoints in the Adhamiya neighbourhood and a car bombing in the eastern district of Palestine Street.
Overall, levels of violence in Iraq have fallen since its peak in 2006-07, but attacks remain commonplace, with 177 people reportedly dying in violent attacks in May.
As a year-end deadline for the withdrawal of 45,000 US troops from the country approaches, some have questioned the ability of Iraqi forces to provide security in their stead.