Car bombs and explosions in cities across Iraq have killed at least 31 people days before provincial elections.

The attacks included two explosions at a checkpoint outside Baghdad's international airport.

No one has claimed responsibility for the attacks, which also happened in Kirkuk, Tuz Khurmato, Samarra and Nassiriya.

Iraqis will vote on Saturday for members of provincial councils in a ballot that is seen as a test of political stability since the last US troops withdrew in December 2011.

A dozen candidates have already been killed so far in campaigning, including two moderate Sunni politicians over the weekend.