The incident occurred overnight on Lake Syamozero, located some 1,000 kilometres north of Moscow in the Karelia region, authorities told Russian news agencies.
“Eleven children and one adult have died,” the spokesman of Russia’s Investigative Committee, Vladimir Markin, said as quoted by RIA Novosti.
The local branch of the emergency situations ministry said that a group of children was on board two boats and one raft that were caught in a storm during the night.Russia’s children’s rights ombudsman, Pavel Astakhov, told RIA Novosti that the children who died were “apparently not wearing life jackets.”
An unnamed source in local emergency services told TASS news agency that the dead children were aged 12 to 15 and had been attending a summer camp nearby.
The emergency situations ministry told RIA Novosti that 36 people had been saved from the water and that the whereabouts of four other people remained unknown.
It was not immediately clear how many people were on the water at the time of the incident.
Moscow mayor Sergei Sobyanin wrote on Twitter Sunday that the 10 dead children were from the Russian capital.
Russia’s investigative committee announced it was opening a criminal case into the incident to probe whether water safety regulations had been neglected on the water.
One of the summer camp instructors has been detained for questioning, the committee said.