The Russian capital was placed on lockdown after the home-made bomb exploded at the busy public transport stop, injuring three women.
Pictures emerged on social media showing smashed glass lying in the street as emergency services scrambled to the bus stop, in central Moscow, to treat the wounded.
Police sources told Russian news agency TASS that an “unknown home-made explosive device” had been used in the attack.
Moscow police spokesman Andrey Galiakberov confirmed that the incident had taken place and said detectives are investigating the circumstances surrounding the explosion.
It is not yet known whether or not the bomb blast is linked to terrorism.
Police sources told news outlet RIA Novosti that the home-made bomb was thrown at a group of people who had been standing at the bus stop, whilst state-owned Russia Today reported that detectives are investigating the case as “hooliganism”.