In a statement, the Prime Minister of the Czech Republic Petr Necas said he was "deeply hit by the tragedy of the gas explosion", the Associated Press reports.
It is not certain what caused the blast in Divadelni Street in the central Prague but it was likely to be a natural gas explosion, police spokesman Tomas Hulan said.
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According to local reports, the repairman had failed to disconnect the power to the escalator before getting to work.
Millwall fans who caused problems at the match against Barnsley could face lifetime bans, the club said.
Counter-terrorism forces, backed by Shi'ite militias on the ground and coalition airstrikes, are moving into the city on several fronts.