A subway train in Moscow has derailed between two stations, killing at least 21 people and injuring more than 130, according to multiple news reports from the Russian capital.
Of the 136 people hospitalised, at least 42 were in grave condition, health officials said on Tuesday.
Several cars left the track in the tunnel during rush hour after a power surge triggered an alarm, which caused the train to stop abruptly.
Over 1,100 people were evacuated from the train, which was stuck between two stations, in a rescue operation that ended more than 12 hours after the accident. One woman taken from the scene died at a Moscow hospital.
A man with a bloody cut on his brow told Rossiya 24 television outside the station that he felt a jolt and the train abruptly came to a halt.
"There was smoke and we were trapped inside," the man said. "It's a miracle we got out. I thought it was the end."
Rescuers managed to airlift the most serious victims to the hospital, where they later died.
According to reports, one of the cars derailed about 200 metres from one of the metro stations. Several images posted on social media sites showed injured commuters being carried by rescuers in stretchers.
While accidents are regular occurrences in the Moscow Metro, deadly incidents are rare.