A US citizen was shot and wounded in eastern Saudi Arabia on Friday, the state news agency SPA reported, adding to security concerns in the world’s top oil exporting nation.

A vehicle carrying two US citizens came under fire in the Eastern Province district of al-Ahsa, one of the main centres of Saudi Arabia’s minority Shia, SPA said, citing a police statement. It was not clear who shot at the vehicle.

The wounded man was taken to hospital and was in a stable condition, it added.

Saudi officials are concerned about the spread of sectarian strife from the conflicts in Yemen, Iraq and Syria. Some leading clerics of Saudi Arabia’s official Wahhabi school of Sunni Islam view Shia as heretics.

In the last attack on Saudi soil targeting Americans, a gunman killed a US citizen and wounded another in the capital, Riyadh, in October 2014.

In November, seven Shia Muslims were shot dead in al-Ahsa as they marked theholy day of Ashoura. Saudi Arabia has arrested the four main suspects and said it believes the attack was ordered by Islamic State (Isis) militants from abroad

Qatif, another centre of the Saudi Shia minority alongside al-Ahsa, has been a focus of anti-government demonstrations in support of Shia who complain of discrimination. The Saudi authorities deny any discrimination.