At least 30 people have been killed in a bombing in the northern Iraqi town of Tuz Khurmato, local officials and medical workers have said.

The offices of a Kurdish political party were targeted.

Security sources said a car bomb blew up at a checkpoint near the local headquarters of the Patriotic Union of Kurdistan (PUK) party.

A truck packed with explosives was subsequently detonated beside a wall.

The attack is the latest in a show of strength by militants who have been regaining ground in Iraq.

Another 18 people were yesterday killed in twin blasts targeting PUK offices in the town of Jalawla.

The Sunni militant Islamic State of Iraq and the Levant (ISIS) group has claimed responsibility for both attacks.

A further 185 people were wounded in the blasts, the force of which destroyed many buildings in the area.

Sources say more bodies are likely to be found beneath the debris.

Tuz Khurmato is around 170km north of the capital Baghdad and lies in territory which both the federal government and the autonomous Kurdistan region claim as theirs.

Both are a target for Sunni Islamist insurgents who in recent days overran two major cities, occupied a university campus in western Iraq and set off a dozen car bombs in Baghdad.

Nearly 800 people were killed across the country in May alone, the highest monthly toll this year so far.