Cellphone video shows the suicide bombing and gun attack on Shi'ite Muslim worshippers that killed at least four people in eastern Saudi Arabia today, according to the interior ministry and witnesses.

The assault on the Imam Rida mosque in the Eastern Province town of Mahasen, a mixed Sunni-Shi'ite district, also wounded at least 18 people.

In a video filmed by an eyewitness inside the mosque, a loud explosion is heard before the mosque's lights go out. Gunfire is heard as people start yelling.

Another video filmed by the same eyewitness shows at least one person lying motionless on the ground.

Describing the scene, the man told Reuters he heard gunfire before hearing a loud explosion and then more gunfire.

There was no early claim of responsibility but it resembled previous attacks by Sunni militants from Islamic State on Shi'ites it considers to be heretics. The oil-producing Eastern Province is home to Saudi Arabia's Shi'ite community.

The attack came less than a month after Sunni-ruled Saudi Arabia executed 47 people, most of them al Qaeda militants convicted of attacks in the world's biggest oil exporting state since 2003, as well as dissident Shi'ite cleric Nimr al-Nimr.

The Saudi interior ministry said security forces prevented two suicide bombers from entering the mosque, where one blew himself up, killing four people. Security forces exchanged fire with the second man and arrested him.

Witnesses said one suicide bomber blew himself up outside the mosque, causing a power blackout inside. They said worshippers overpowered a second attacker after he opened fire in the mosque where 200 people were performing Friday prayers.

Another witness, speaking to Reuters by telephone, said a third attacker was believed to be involved in the attack and that he may have fled or disappeared.