RIYADH, Saudi Arabia — A Saudi security officer was killed in an operation to free three foreign laborers taken hostage by a gunman in the capital, Riyadh, according to a police statement carried by the official Saudi Press Agency on Monday.

Saudi police said an attacker armed with an assault rifle seized the workers Sunday evening near a mosque and opened fire when surrounded by police. Police said they were able to free the hostages after a heavy exchange of gunfire.

The attacker was wounded and captured in the shoot-out. In addition to the slain officer, a civilian and a member of the security forces were also injured.

Security officials did not disclose the identity of the attacker, possible motives for the attack or the nationality of the hostages.

Also on Sunday, a Saudi policeman was shot and killed in the eastern town of al-Awamiya by an unidentified assailant. The town is heavily populated by minority Saudi Shiites and is the hometown of revered Shiite cleric Nimr al-Nimr, an outspoken government critic who was sentenced to death in October for inciting violence and sectarian strife — charges which he denies and which have outraged his supporters.

The Eastern Province was rocked last month when seven Shiite worshippers were shot dead in an attack that police say appears to have been carried out by supporters of the extremist Islamic State group. Police have also arrested several people in the shooting and wounding of a Danish man in the capital Riyadh in November, an attack which was claimed by IS supporters.

There are growing concerns about militant attacks in the kingdom in retaliation for its role in the U.S.-led coalition battling the Islamic State group in Iraq and Syria.

Saudi King Abdullah met with Jordan's King Abdullah II in Riyadh on Sunday to discuss regional issues, according to the Saudi Press Agency. Jordan is also part of the U.S.-led group of nations conducting airstrikes against the IS group.