The St Petersburg metro explosion has been condemned as a "barbaric and cowardly terrorist attack" by the UN Security Council.
Offering condolences to the victims of the blast - which happened between Sennaya Ploshchad and Tekhnologichesky Institut underground stations - council members released a statement saying the "perpetrators, organizers, financiers and sponsors of these reprehensible acts" should be brought to justice.
The seven people were from Central Asian countries and investigators say they were recruiting for IS.
The bombing of a subway train in Russia has drawn condemnation from world leaders.
A blast has ripped through an underground train in Russia's second-largest city on Monday.