As many as 40 people have been reported injured in a blast in the Czech capital city of Prague.

Police say it has damaged a building and there are people trapped under the rubble. Officers say they do not know what has caused the explosion. But a spokesman said it was probably gas-related.

15 people are thought to have been inside the building at the time of the blast.

A fire department spokeswoman said there had not been reports of any deaths but neighbouring buildings have been evacuated.

Photographer Walter Novak is at the scene.

"There was just rubble on the street, some damaged cars, dust - some people been a little bit scared - nobody knows what happened" he said.