World Bulletin / News Desk
In the message sent on Monday, Erdogan condemned the "horrific" attack which has claimed at least 14 lives and injured dozens, the source said on condition of anonymity due to restrictions on talking to the media.
"I would like to express that Turkey, a country which has struggled with terrorism for many years, stands by Russia against this treacherous terror attack," Erdogan said in his message.
The Turkish president also conveyed his condolences to the Russian people and to the families of the victims and wished a "speedy" recovery to the injured.
According to Russia's National Anti-Terrorism Committee, Monday’s blast tore through a train at 2.40 p.m. local time (1140GMT) on Monday as it was traveling between Sennaya Ploshchad and Technological Institute stations.
The Russian Investigative Committee later described the explosion as a "terrorist attack".