Among the almost 50 people injured in the explosion in the St. Petersburg metro, at least four are said to be in a critical condition in hospital.
Emergency teams are also providing psychological support to many commuters caught up in the panic.
Veronika Skvortsova, the Russian Health Minister, told reporters: “All night the number of patients changed, wounded people continued to present themselves at the hospital, coming from the site of the attack.
“And at the same time some of the patients had received treatment and could return home”.
The driver of the train hit by the blast carried on to the next station, which emergency services say may have saved lives.
Victims were able to be quickly tended to and taken to waiting ambulances.