A gunman has opened fire inside a cathedral on the eastern Russian island of Sakhalin, killing a nun and a churchgoer, say reports.
An employee at a private security firm was detained at the scene in the main city of Yuzhno-Sakhalinsk.
The motive of the man, who is said to be about 25 years old, were not clear.
There was no apparent link to the Winter Olympics taking place in Sochi about 7,500km (4,700 miles) to the west.
The Investigative Committee - Russia's main federal investigating authority - said psychiatrists would try to determine the suspect's mental condition, reported Reuters news agency.
Reuters quoted the regional leader of the Russian Orthodox Church, Archbishop Tikhon, as saying a prayer service would be held at the cathedral later on Sunday.