A suicide bomber from Kyrgyzstan was behind the explosion that killed 11 people and injured dozens more in a Saint Petersburg metro station, security services in the former Soviet republic of Kyrgyzstan said on Tuesday.

“The suicide bomber in the Saint Petersburg metro was a Kyrgyz national Akbarjon Djalilov... born in 1995,” a spokesman for the country’s security services told AFP.

“It is probable that he acquired Russian nationality,” he said.

Russia’s Investigative Committee said it was probing an “act of terror” over the blast that rocked the metro in the country’s second big city on Monday afternoon, but added it would look into all other possible causes of the blast.

There was no immediate claim of responsibility for the explosion, which comes after the Islamic State group called for attacks on Russia in retribution for its military intervention in Syria.