A gunman has killed two people and wounded six others in a shooting at an Orthodox cathedral on Russia's Sakhalin Island, off the country's eastern coast, according to Reuters news agency.

Russia's state-run news agency, RIA, reported that a man opened fire, killing a nun and a churchgoer on Sunday at the main cathedral in the city of Yuzhno-Sakhalinsk.

Most of the wounded were shot in the legs and their lives were not in danger, RIA quoted Archbishop Tikhon, the regional leader of the Russian Orthodox Church, as saying.

The gunman was arrested, the Federal Investigative Agency said, adding that he worked as a security guard in Yuzhno-Sakhalinsk.

No Sochi connection

So far no motive for the attack has been reported.

This attack came only days after a teenager shot and killed a teacher and policeman at a school in northern Moscow.

Security forces in Russia are on high alert due to concerns over possible attacks at the Winter Olympics in Sochi.

But the games are taking place thousands of kilometres away from Yuzhno-Sakhalinsk and there was no apparent link between Sunday's shooting and Sochi, according to Reuters.

Archbishop Tikhon said a prayer service will be held later on Sunday for the victims, adding that the church would have to be cleaned of victims' blood and blessed.