Causes of St Petersburg subway blast are still unknown, all versions, both domestic and terrorism, are being considered, TASS reported quoting Russian President Vladimir Putin.

He noted that received reports of intelligence agencies on two blasts that rocked metro in St Petersburg.

“I have already talked to the heads of special services, to the director of the Federal Security Service,” he said at a meeting with President of Belarus Alexander Lukashenko.

According to unofficial data, at least 10 people were killed and 20 more were injured in two explosions.