A suicide bomber blew himself up at a Shi'ite mosque in eastern Saudi Arabia during Friday prayers, residents said, killing and wounding several people.

One witness described a huge explosion at the Imam Ali mosque in the village of Sl-Qadeeh. He estimated there were at least 30 casualties in the attack, where more than 150 people were praying.

"We were doing the first part of the prayers when we heard the blast," Kamal Jaafar Hassan, one worshipper, told Reuters by telephone from the scene.

The Saudi state news agency confirmed an explosion had occurred at a mosque in eastern Saudi Arabia and said more details would be provided later.

Pictures posted on social media showed bloodied victims being taken away on stretchers. - Reuters