The Russian leader expressed his condolences and said a terror attack would be considered “first of all”.
Mr Putin, who was in St Petersburg for a meeting with Belarussian leader Alexander Lukashenko, said: “The causes of this event have not been determined yet, so it’s too early to talk about possible causes.
“The investigation will show. Certainly, we will consider all variants, common, criminal, first of all, of a terrorist nature.
“The city authorities, and, if required, the federal authorities, will take all necessary measures to support the families of those killed and those injured.”Earlier reports suggested there had been two explosions, however later reports say there was one between both stations.
A second unexploded device is believed to have been found at the Ploshad Vosstaniya metro station.
The horror attack between Sennaya Ploschad station and Tekhnologichesky Institute station has left 10 people dead and 50 people injured.
Moscow’s metro system has also been shut down as a precaution.