Romanian President Klaus Iohannis has hinted at a breach of safety regulations at a Bucharest nightclub where a fire and stampede on Friday night left 27 people - mostly youngsters - dead.

"We already have indications that the legal regulations had not been respected," Iohannis said, calling for authorities to carry out a speedy and thorough investigation into the tragedy.

The scale of the blaze and subsequent panic, which saw nearly 200 people injured, has left many Romanians shocked.

The government declared three days of morning for what's been described as the worst bloodshed since the 1989 anti-Communist revolution. An emergency cabinet meeting was also held on Saturday morning.

Twenty-six people died in the club and one died in hospital, officials said, adding that out of the injured, 146 people were hospitalized for burns, smoke inhalation and other injuries.

Ten people remain in a critical condition, hospital sources told Agence France Presse.

The fire broke out at around 11p.m. local time (21:00 UTC) on Friday at the Colectiv nightclub, where as many as 400 young people had gathered for a pre-Halloween gig by the rock group Goodbye to Gravity.

The band's singer and bassist were also said to be in a serious condition, according to local reports.

Night of 'horror'

Some club-goers told Antena 3 TV that the blaze started when a pyrotechnic show went awry at the club at a former factory. They said there was only one exit.

Other witnesses told Digi 24 television that a spark on stage ignited some polystyrene decor which quickly filled the club with thick smoke.

Another told Associated Press that club-goers were taken by surprise at how fast the fire grew and panicked as it spread.

More than 500 firefighters, ambulance crew and police were mobilized.

Prosecutors said they are investigating possible manslaughter charges. Police spent all night in the club investigating the incident and questioning the club's owners.

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

Fireworks and restricted exits have been a lethal combination in many nightclub fires around the world.

In one of the worst such disasters, 156 clubbers in the Russian city of Perm died in 2009 in a blaze caused by pyrotechnics, and 83 were injured. Seven people were jailed for up to nine years after the tragedy.

mm/ng (AP, AFP, Reuters)