Islamic State is not a significant threat in Saudi Arabia, the US military said, as it declined to speculate on the Sunni militant group's claim of responsibility for a deadly bombing at Shi'ite Muslim mosque.

"In terms of Saudi Arabia and (Islamic State), we have no indication that they pose a significant threat at this time," said Colonel Patrick Ryder, a spokesman for the Pentagon's Central Command, which oversees US forces in the Middle East.

Friday's blast killed four people and was the second attack claimed by the Sunni militant group in a week in the world's top oil-exporting country.-Reuters