Saudi Arabia on Monday executed a citizen convicted of killing a policeman, the interior ministry announced, bringing to 146 the number of death sentences carried out in the kingdom this year.

Ayed al-Jahdali was convicted of shooting dead a policeman who was trying to arrest him for drug trafficking, the ministry said in a statement carried by the official SPA news agency.

He was executed in the western Mecca region, it said.

Saudi executions are usually carried out by beheading with a sword.

According to AFP tallies, his case brings to 146 the number of locals and foreigners executed in the conservative kingdom this year, compared with 87 in 2014.

Rights experts have raised concerns about the fairness of trials in the kingdom.

Iran on Sunday summoned Saudi Arabia's charge d'affaires in Tehran after the Gulf kingdom executed three Iranians convicted of drug trafficking, Iran's official IRNA news agency reported.

London-based Amnesty International says Saudi Arabia had the world's third-highest number of executions last year, far behind China and Iran, but ahead of Iraq and the United States.

Under the kingdom's strict legal code, murder, drug trafficking, armed robbery, rape and apostasy are all punishable by death.