Romania's government has declared a three-day national mourning after an overnight fire ripped through a nightclub in the capital Bucharest, killing at least 27 people and wounding more than 180 more.

The fire broke out at about 11pm on Friday night at the Colectiv nightclub in the Romanian capital, with hundreds of people inside attending a rock concert.

Victor Ionescu, who was at the club with his girlfriend, told Antena 3 TV by telephone that there were huge flames after the explosion.

"People were fainting - they were fainting from the smoke. It was total chaos, people were trampling on each other," he said.

A young man filmed by Antena 3 said that flames engulfed clubbers, burning their skin and hair.

The official death toll was raised to 27 early on Saturday morning and Deputy Interior Minister Raed Arafat said the toll may still climb further.

Journalist Sanda Nicola, reporting from Bucharest, told Al Jazeera that the Romanian health ministry has put out a notice calling for blood donations.

"The club was packed with about 300 people inside for a rock concert with a pyrotechnic show," she said.

"Some of those being admitted to hospital have burns all over their bodies. Most of the victims were teenagers and students.

"Paramedics say that many of the people involved were foreigners who did not speak Romanian."

Nicola said the cause of the fire has not yet been confirmed, but said it is believed that there had been a problem with the pyrotechnics.

She said that some witnesses reported that fireworks hit the roof of the club, sparking the blaze.

A young woman who was released from the hospital after minor injuries described the club bursting into flames.

"In five seconds, the whole ceiling was all on fire. In the next three, we rushed to a single door," she told Antena 3.

"There was a stampede of people running out of the club," a man who escaped without shoes told the Reuters news agency.

Romanian President Klaus Iohannis said in a statement: "I want to assure you of all support from rescuing forces and ask you to trust they put all efforts to limit the impact of this catastrophe."

The Romanian health ministry has put out a notice calling for blood donations [EPA]

Source: Al Jazeera and agencies