Russia's Federal Security Service (FSB) on Wednesday detained members of Allya Ayat, a religious group originating in Kazakhstan, banned and labeled as "extremist" under Russian law, in the city of Rostov-on-Don, TASS reported.

Russian authorities are on high alert following a mass shooting at a concert hall near Moscow last Friday, where at least 140 people were killed. The Islamic State has claimed responsibility for the attack.

(With input from Reuters)