TIKRIT, Iraq (Reuters) - At least four policemen were killed and 11 wounded by two roadside bombs that targeted police convoys in separate attacks in northern Iraq on Sunday, the service and medical sources said.

Two died and eight were wounded when a bomb hit a bus carrying police on their way to work near the town of Shirqat, its police chief colonel Majeed Ghatran said.

Another bomb struck a second group of officers that was heading to the location of the first explosion, killing two and wounding three, he said.

No organization claimed responsibility for the bombings.

Islamic State militants have carried out guerrilla-style attacks in the area since their military defeat in Iraq in December 2017.

Reporting by Ghazwan Hassan in Tikrit; Additional reporting by Adam Hadi in Diyala; Writing by Ahmed Rasheed; editing by John Stonestreet