Twenty-seven people - mostly teenagers and young people - have been killed after fire broke out at a nightclub in Bucharest, officials said.

The blaze took hold at the Colectiv club on Friday night, causing a stampede for the exit, the BBC News reported.

Emergency response chief Raed Arafat said 155 people were being treated in hospitals in the Romanian capital.

The fire is believed to have been caused by fireworks that were let off inside the club.

"The only information we have is that fireworks were used in the club and after that the tragedy happened. Of course, this is under investigation," Arafat told the BBC.

The pyrotechnics were reportedly part of a show by a heavy metal band.

Witnesses said a spark on the stage ignited some of the polystyrene decor. A pillar and the club's ceiling caught fire and there was an explosion and heavy smoke, they added.

Up to 400 people may have been inside the club, which was hosting a free rock concert.

A witness quoted by Romania's state news agency said terrified concert-goers had to break the second door down to escape.

Romanian Prime Minister Victor Ponta said he was cutting short a visit to Mexico to return to Bucharest.

Romania's President Klaus Iohannis wrote on his Facebook page that he was "deeply grieved by the tragic events that happened this evening in downtown."

Source: MENA