Prague expolsion
Firefighters search the area after an explosion in Prague (Reuters)

A powerful blast has rocked a building in central Prague, injuring dozens and leaving people trapped beneath tonnes of rubble.

Police spokesman Tomas Hulan said it was not clear what triggered the explosion in the capital of the Czech Republic capital but it was likely to have been a natural gas explosion.

Up to 40 people were injured, the head of the rescue service, Zdenek Schwarz, said. Four are reportedly in critic conditions.

The explosion hit a building in the central Divadelni Street. Police cordoned off the area and firefighters were searching for survivors under the rubble.

"There was glass everywhere and people shouting and crying," said student Vaclav Rokyta.

Police said about 15 people were inside the building at the moment of the explosion, Russia Today reported.

The building housed an art gallery and an office of the International Air Transport Association (IATA).

The blast reportedly smashed windows in buildings as far as 100 metres away.

"I was in the bathroom - no windows, the door was closed. If I had been in my bed I would have been covered in glass," said ZB Haislip, a student from the US state of North Carolina, who was in a nearby building.

"We were sitting in the classroom, when we heard a huge bang and everyone rushed to the window to see what was happening. Students from the next class started running and then we saw smoke," an eyewitness told Russia Today.

Neighbouring buildings have been evacuated. Early reports suggest a leaking gas pipe might have caused the blast.

Czech prime minister Petr Necas said he was "deeply hit by the tragedy of the gas explosion".

More to follow...

Injured people leave the area after an explosion in Prague (Reuters)