A small bomb exploded outside a highway patrol station in eastern Saudi Arabia, injuring a policeman, official media said on Friday.

A small bomb exploded outside a highway patrol station in eastern Saudi Arabia, injuring a policeman, official media said on Friday.

The attack happened late Thursday in the Al-Ahsa region, the Saudi Press Agency said, citing a provincial police spokesman.

One member of the police force received "a minor injury" and five vehicles were damaged, the spokesman added.

"Authorities started criminal investigations," he added.

In January a suicide bomber attacked a Shiite mosque in Al-Ahsa, killing two people and wounding seven during Friday prayers.

It was the latest assault after earlier shootings and bombings claimed by the Takfiri group, ISIL.