A gun found on a man who was shot dead by police in south Russia was used in the murder of a priest in Moscow last year, investigators said on Tuesday.

The man, who was carrying a Russian passport in the name of Beksultan Karybekov, had been detained by police in the North Caucasus republic of Dagestan in connection with an unrelated incident.

"The detainee offered armed resistance - he grabbed a gun and threw a grenade, after which he opened fire with a hand gun at police. He was killed by their return fire," Investigation Committee spokesman Vladimir Markin said.

The gun found on his body was used in the killing of priest Daniil Sysoyev, who was shot dead by a masked gunman in St. Thomas' Church in southern Moscow on November 19, 2009.

Sysoyev was known for his active missionary work in converting Muslims and people seeking to quit religious sects into Christianity. His assistant, Vladimir Strelbitsky, was badly wounded in the attack.

The murder stirred a wave of condemnation from all religious groups in Russia, and demands for better security for the clergy.

"Police have incontrovertible evidence that this very gun was used to kill Daniil Sysoyev," Markin said.

A law enforcement source told RIA Novosti earlier that police had identified a suspect in the murder of Sysoyev, but that he was most likely abroad.

MOSCOW, March 16 (RIA Novosti)