Police cordon off part of central Prague following an explosion that injured as many as 40.
Witnesses say around a dozen people were treated at the scene by emergency services.
The blast, probably caused by gas, came from a building owned by Czech Air Navigation Services.
Police said about 15 people were in the building at the time of the explosion.
Many surrounding buildings were evacuated, including the National Theatre.
This pensioner says she heard an incredible explosion and thought her building would collapse.
The fire department says there are no reports yet of fatalities.
