Survivors of a deadly nightclub fire and stampede in Romania say the lead singer of the heavy metal band on stage first made a joke about the fire before it engulfed the basement club in downtown Bucharest.

Hundreds of young people had gone clubbing at the hip Colectiv nightclub on Friday to enjoy a free concert by the Goodbye to Gravity metal band. The evening ended in horror, as the inferno caused a panic that killed 27 people and injured 180 others.

Around 146 people remained hospitalised, some in critical condition suffering from burns and smoke inhalation.

Officials expect the death toll to rise in what is the worst disaster of its kind ever in Romania.

Premier Victor Ponta cut short a visit to Mexico to return to Bucharest and declared three days of mourning for the victims starting immediately.

By yesterday afternoon, four of the dead had still not been identified, media reported. TV stations posted a number for families to call to find out about the tragedy.

An Italian woman, two Spanish citizens and a German man were among the injured, the Romanian Intelligence Agency said.

Witnesses told Antena 3 TV that between 300 and 400 mostly young people had been at the club, housed in a former factory, when a pyrotechnical show went awry.

They said there was only one exit