ISIS claimed responsibility for the attack on Twitter. The statement on twitter included details of the operation and a photograph of the alleged bomber.
At least 21 people (earlier reported 30) were killed when a suicide bomber blew himself up at a Shia mosque in eastern Saudi Arabia while the Friday prayer was undergoing.
A huge explosion rocked at the Imam Ali mosque in a village in Saudi Arabia, BBC reported citing. [Returned ISIS militants likely to launch chemical weapon attack: expert]
ISIS has captured parts of Iraq and Syria for what it calls its Islamic caliphate, has not carried out many attacks in Saudi Arabia. [Why do Islamic fundamentalists hate anything old and beautiful]
The most recent attack was carried out by the group in January when Saudi Arabia said that ISIS fighters broke through Saudi defenses on the Iraqi-Saudi border, killing three Saudi soldiers.
Shiite Muslims are a minority in Saudi Arabia, where 85% to 90% of the citizens are Sunni.