Two Saudi men operating under orders from members of the extremist Islamic State group in Syria are suspected of being behind the killing of two policemen in the capital Riyadh, the kingdom's Interior Ministry said Friday.

The April 8 shooting is the fifth attack believed to have been carried out by IS members inside the kingdom. It also brings the total number of civilians and security personnel killed in IS-related violence in Saudi Arabia to 15.

Saudi Arabia is taking part in U.S.-led coalition airstrikes on IS militants in Syria. The group has retaliated with calls for attacks inside the kingdom.

Interior Ministry spokesman Maj. Gen. Mansour al-Turki told a press conference that one suspect was under arrest and that the second was still at-large.

He said the suspect under arrest sent pictures of the deadly attack to IS group members in Syria and coordinated the attack with them. Al-Turki said IS militants in Syria recruited him through the Internet.

"It is upon everyone... to protect your son or daughter from such ideas, and to live with them, live among them in their daily lives, monitor them and give them advice," he said. "This is a community responsibility."

The suspect still at-large, named as Nawaf al-Enezi, is believed to be an experienced militant, al-Turki said. The police are offering a 1 million Saudi riyal ($267,000) reward for information that leads to his arrest.

IS group members have previously been blamed for an attack on Saudi border guards near Iraq that killed three security personnel in January and a shooting of Shiite worshippers in al-Ahsa in the Eastern Province in November that killed eight people.

Two police officers died in raids that led to the arrests of suspects behind the al-Ahsa shooting.

Other IS attacks in the kingdom in recent months include the shooting and wounding of a Danish citizen in Riyadh and a separate shooting directed at police in the city that did not lead to deaths, he said.

Al-Turki told The Associated Press that a total of seven IS-linked suspects have been killed by police.