Twenty people died and scores more were hurt after a train derailed in Moscow's packed metro during rush hour on Tuesday in the worst accident to hit one of the world's busiest subways.
Russian television described scenes of chaos and panic on the capital city's famed system, saying passengers fell like dominoes when the train braked abruptly and three carriages derailed.
President Vladimir Putin, who is currently on a trip to Brazil, was informed of the tragedy that put a huge strain on the city of some 12 million and snarled traffic on its notoriously clogged roads amid a heat wave.
Sirens wailed as dozens of ambulances rushed to help treat the wounded and helicopters buzzed overhead to evacuate those with the most serious injuries, AFP journalists said at the scene outside the deep Park Pobedy metro station in western Moscow.
Nineteen people perished at the scene and another passenger died of her injuries in hospital, a health ministry spokesman said in televised remarks, adding that nearly 130 people were hospitalised.
Rescue teams were working to free about five people believed to be stuck in a train underground, Moscow deputy mayor Pyotr Biryukov told journalists at the scene. "There are those who've been trapped, they are showing signs of life," he said. Around half of those who were hospitalised were in a serious condition, authorities said.
"I thought it was the end," one passenger said on television. "We were trapped and only got out through a miracle.
Passengers said smoke quickly spread through the carriages and rescue workers treated them with oxygen.
The accident took place as temperatures outside soared to 28 degrees Celsius.
Authorities said it would take 24 hours to deal with the aftermath of the accident.
As news of the crash spread, the hashtag #metro quickly become one of the most popular on Twitter in Russia.
Citing preliminary information, the Investigative Committee said the accident happened due to a train braking abruptly because of a false alarm triggered by a supply voltage dip.
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