Seven people including a two-year-old child were killed on Thursday in a gas explosion in a housing block in the city of Novosibirsk in Siberia, the regional health ministry said, in Russia's second fatal gas explosion in three days.
Russia's Investigative Committee, which is responsible for major crimes, said it had opened an investigation and detained two people who had performed gas maintenance work in the building several days before.
Video published by Russia's emergencies ministry showed a section of a multi-story residential building largely destroyed, with the building's facade missing. The ministry's head flew to Novosibirsk to oversee the response.
Regional health authorities said seven people remained in hospital, where they were being treated for injuries sustained in the blast. It said two were in a critical condition.
In a separate incident on Tuesday, at least five people were killed in a gas explosion that ripped through a five-floor building in the town of Yefremov, south of Moscow.
Gas explosions are relatively common in Russia because of ageing infrastructure and lax safety regulations surrounding gas use.