ISIS claims 2nd Saudi mosque attack

(CNN) ISIS has claimed it carried out another deadly suicide attack on a Shiite mosque in eastern Saudi Arabia. It's the second attack in the kingdom in a week for which the terror group has taken responsibility.

A Saudi source with detailed knowledge of the investigation said that a suicide bomber detonated explosives outside the Imam Hussein mosque in Dammam, a coastal city about 70 kilometers (45 miles) from the Persian Gulf island nation of Bahrain, shortly after noon (5 a.m. ET) Friday.

The attacker -- dressed in traditional female clothing as a cover-up -- had been challenged by Shiites who had volunteered to search those going into the mosque in the wake of the previous week's attack on the Imam Ali mosque in the village of Qudayh, according to the source.

The bomber then set off explosives -- killing himself and three Shiite worshipers, the source said.

A Saudi Interior Ministry spokesman gave a slightly different account, saying "security authorities" went up to a suspicious vehicle as it was parking adjacent to the mosque, according to the official Saudi Press Agency.

"When the security men approached the car, it exploded, killing four people -- one of them believed to be the driver -- and spreading fire to a number of cars," the spokesman said.

Friday's carnage happened in the predominantly Shiite neighborhood of Anoud in Dammam, the capital of Saudi Arabia's oil-rich Eastern Province. It is one of the few Shiite population centers in a country in which 85% to 90% of citizens are Sunni, the other major Islamic sect.

ISIS claimed responsibility for the attack, according to a statement posted to Twitter by its supporters -- showing the terrorist group's efforts to bring violence and chaos to another Middle East country after its successes in Syria, Iraq and Libya.

"In a blessed martyrdom operation, a Polytheistic monument was targeted, that (the Shiite community) established in Sunni areas to spread out their polytheism," ISIS reportedly said, identifying the suicide bomber as Abu Jned al Zazrawi.