Riyadh, Saudi Arabia: A blast ripped through a Shiite mosque killing at least 30 people in eastern Saudi Arabia on Friday, authorities said, in what an activist said was a deadly suicide bombing.

The interior ministry said a large explosion hit the mosque in Kudeih in Shiite-majority Qatif province during the Jumma prayers.

A news websites in eastern Saudi Arabia posted photographs of bodies lying in pools of blood.

Qatif hospital issued an urgent call for blood donations after the attack and called in off-duty staff to cope with the high number of casualties, the activist said.

An interior ministry spokesman said an investigation has been opened and more details of the explosion would follow.