At least 15 children on a summer camp in north-east Russia drowned when their boats capsized in a storm on a lake, investigators and Russian media reports say.

The accident happened overnight on Lake Syamozero, close to the border with Finland, according to Vladimir Markin, a spokesman for Russia’s investigative committee.

The TASS news agency said 15 children died.

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“There are no adults among the victims,” Mr Markin said in a statement.

Four members of the camp staff had been detained for questioning following the tragedy, he added.

The children, who were aged between 12 and 15, were “apparently not wearing life jackets”, Russia’s children’s rights watchdog, Pavel Astakhov, told the RIA Novosti agency.

The group was taking part in a summer camp close to the lake.

The Emergencies Ministry said the children were sailing on two boats and a raft when they got caught in a storm after nightfall.

Rescuers saved more than 30 people, the Ministry told RIA Novosti.

Moscow mayor Sergei Sobyanin wrote on Twitter on Sunday that 10 of the dead children were from Moscow.

Investigators have opened a criminal probe into the incident to determine whether water safety rules were followed.