MOSCOW, November 20 (RIA Novosti) - An unidentified gunman killed a well-known Russian Orthodox priest and wounded another clergyman in a church in southern Moscow.

According to investigators, the killer, who was wearing a face mask, entered the St. Thomas the Apostle church on Thursday night and opened fire with a 9-mm automatic pistol, deliberately targeting its rector, Daniil Sysoyev. The priest died in a hospital after sustaining head and chest wounds.

"It is a terrible tragedy. A murder of a priest in a church, as any other murder, is a grievous sin and a direct violation of the Ten Commandments," Vladimir Legoyda, a spokesman for the Russian Orthodox Church said.

Sysoyev, 35, was well-known for his missionary activities and the fight against sectarianism and occultism.

Investigators suspect that the murder was premeditated and had religious motives because Sysoyev had received death threats on several occasions in the past.