Toll rising in Moscow subway crash
A subway train has derailed deep below Moscow's streets, mangling crowded carriages at the height of the morning rush hour and killing at least 21 people.
Russian officials said 136 more were being treated in hospital, many with serious injuries.
The Russian capital's airports and transit systems have been a prime target for terrorists over the past two decades, but multiple officials dismissed terrorism as a possible cause.
The Moscow Metro is famous for its palatial interiors with mosaics, chandeliers and marble benches. Park Pobedy, where the derailment occurred, is Moscow's deepest metro station - 275ft below the surface - which made the rescue particularly difficult. The station serves the vast park where Russia's Second World War museum is located.
It is unclear what caused the train to derail. Lines of inquiry included a fault in one of the carriages or the sinking of the roadbed, according to Vladimir Markin, spokesman for Russia's top investigative body. He rejected earlier suggestions that a power surge triggered an alarm, causing the train to stop abruptly.
Of the 136 people in hospital, at least 42 were in grave condition, health officials said. One citizen of China and one from Tajikistan were among those killed, Russian news agencies quoted city officials as saying.
More than 1,100 people were evacuated from the train, which was stuck between two stations, in a rescue operation that lasted at least 12 hours.
By evening, rescuers had recovered all but two of the bodies trapped in the wrecked carriages, said Yury Akimov, deputy chief of Moscow's emergency services. One woman taken from the scene died in hospital.
In video released by the Emergency Situations Ministry, several wrecked carriages looked almost coiled, occupying the entire width of the tunnel. Workers were trying to force open the mangled doors of one car to retrieve bodies.
Russian officials rushed to open an investigation into the accident. President Vladimir Putin, who is in Brazil, demanded a detailed investigation and asked the country's top investigators to open a criminal case, his spokesman told Russian news agencies.
Mayor Sergei Sobyanin told reporters that unnamed officials will not only be fired but also charged with crimes, though he would not say what charges they might face. Prime minister Dmitry Medvedev offered his condolences for the victims and their families.
Witnesses told Rossiya 24 television that they felt a sharp impact that knocked them off their feet and hurled them across the train cars.
"Everybody spun to one side," said one witness. "There was a sharp brake, and smoke was in the air. People couldn't leave for a long time. The way was blocked."
While technical glitches are regular occurrences in the Moscow Metro, the subway has not seen deadly accidents in decades.
Terrorism is another matter. More than 100 people have been killed in bombings on Moscow's subway trains or near stations since 2000, including two bomb blasts on the same day in 2010 that killed 40 people.