Russia arrested 11 people on suspicion of involvement in Friday's terrorist attack on a concert hall in Moscow.

The Kremlin said in a statement that the head of the Russian Federal Security Service, Alexander Bortnikov, told Putin that they had arrested 11 terrorists, four of whom were directly involved in the Moscow attack.

According to the statement, Bortnikov told Putin that they were working to expose all those involved in the attack.

At least 115 people were killed and more than 100 injured in a terrorist attack on a concert hall in Moscow's Karkus City on Friday.