An unheard “Islamic State” group branch with links to Bahrain has purportedly claimed responsibility for the attack.

Friday Night an ISIS gunman wearing an explosive belt killed five Mourners and wounded nine others in a deadly gun attack at a Shiite mosque in eastern Saudi Arabia.

The gunman was shot dead before he could detonate the explosives, according to State TV.

New ISIS branch calling itself 'Bahrain Province' In a statement posted online claimed its gunman, named Shuja al-Dosari, used a Kalashnikov rifle to attack Shiites in their place of worship.

This is the third ISIS branch to appear in the Arabian Peninsula this year. Two other branches in Saudi Arabia have claimed responsibility for previous attacks on Shiites and security forces that killed nearly 70 people.

The name of the so-called Bahrain Province branch of the ISIS appears to be in reference to the historic area of Bahrain, which once encompassed the current island-state and parts of what is now the oil-rich eastern region of Saudi Arabia.

The kingdom's eastern region and Bahrain are predominantly Shiite, though Saudi Arabia is majority Sunni and Bahrain's rulers are Sunni, according to The Mail.

HB/V1