At least three people were killed and 21 were injured in an explosion outside a restaurant near Kudrinskaya Square in central Moscow.
The blast occurred at about 8pm local time.
Russia’s National Anti-Terrorism Committee said a woman carrying an improvised explosive device tried to enter the restaurant.
The committee said a security guard stopped her at the entrance and the device then detonated outside.
It said the woman, the guard and a restaurant guest were killed.
A private event was under way inside the restaurant at the time of the blast.
The restaurant said the explosion was outside its entrance, contradicting early claims that it had occurred in the kitchen.
Security forces temporarily closed major roads around the square.
A cycling event planned for that night was cancelled.
Russia’s central investigative authority has opened an investigation.
No group was identified in the supplied evidence as claiming responsibility, and a motive was not established.