Those thought to be behind September's deadly blast in Vladikavkaz, in Russia’s republic of North Ossetia, have been arrested.
The powerful car bomb claimed 19 lives and injured over 200 people.
The Head of Russia’s Federal Security Service, Aleksandr Bortnikov, said the case has now been solved.
“Three suspects have been arrested and they are now in jail,” he told journalists.
Bortnikov added that one of those held is Isa Hashagulgov, who is thought to have masterminded the attack. He is said to be a close ally of the self-proclaimed former Chechen militant leader Doku Umarov.
According to Bortnikov, Hashagulgov's gang was allegedly behind more than ten bombings in the neighbouring republic of Ingushetia and numerous attacks on police.
Two other suspects in the Vladikavkaz case were killed after putting up armed resistance.