Lyubov Kovalyova told reporters in Minsk she had received notification from Belarusian authorities her son, Vladislov, had been put to death for his role in last year's blast in the city that left 15 commuters dead and hundreds injured.
Kovalyova and Dmitry Konovalov were convicted in November of carrying out the bombing. The court said in its ruling the pair were "explosives enthusiasts" who posed a threat to society. Russia's RIA Novosti news agency said Konovalov's status was not known.
Lyubov Kovalyova maintained her son's innocence Saturday, telling reporters he had been railroaded by Belarusian authorities.