Riyadh: 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.
Most of Saudi Arabia`s minority Shiites live in the kingdom`s Eastern Province which includes Al-Ahsa, an oasis region where much of the kingdom`s oil reserves are located.
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 on members of the kingdom`s minority community, after earlier shootings and bombings claimed by the Islamic State (IS) Sunni jihadist group.
IS has also claimed attacks on Saudi security forces, most recently early this month when a police colonel was shot dead in the Riyadh area.
Residents have told AFP that criminal activity including the drug trade has also been linked to attacks on police in the east.
Earlier this year unrest including gunfire, burning tires and explosions shook the eastern town of Awamiya after the execution of prominent Shiite cleric Nimr al-Nimr on January 2.
He was a driving force behind protests that began in 2011 among Shiites and later developed into a call for equality in the Sunni-dominated kingdom.