RIYADH: A shooting at a Shia mosque in eastern Saudi Arabia killed four people and wounded seventeen others Friday during prayers, security officials and a witness said, the latest violence to strike the region. The attack struck the Imam Reza Mosque in the neighborhood of Mehasin during prayers. Images on social media showed wounded people lying on the mosque’s floor. The security officials said the four deaths were an initial toll. They spoke on condition of anonymity as a formal announcement had yet to be made. An activist, citing witnesses, said earlier that an explosion was followed by gun attack on Imam Reza Mosque in the town of Mahasen in al-Ahsa region in the eastern province. Residents said security forces were exchanging gunfire with five ‘terrorists’. Mohammed al-Nimr said the attack struck the mosque during Friday prayers.