The Romanian president says safety regulations appear to have been broken in a Bucharest nightclub that went on fire - killing at least 27 people, with as many as 180 others wounded.

The fire unfolded at a Halloween party at the Colectiv club, and up to 400 young revellers were packed into the building's basement.

It is believed that pyrotechnics used during a live rock concert inside the venue misfired because they were poorly fitted.

The spark ignited an acoustic pillar cased in polystyrene, causing fire to spread to the ceiling and the club to fill up with smoke.

There was only one emergency exit available, and many revellers did not immediately react because they thought the flames were part of the show.

"It took two or three seconds to ignite the whole roof," Alexandru Alexe said.

The social activist alleged that "valuable time was lost" as firefighters entered the burning building from the wrong entrance - and also claimed ambulance crews took 30 minutes to arrive after the first emergency call was made.

Teenagers as young as 14 were inside the club when the fire began, and have been treated by specialists.

Overnight, 155 people were being cared for across 10 hospitals - and at one treatment centre, 14 patients are in a critical condition.

Another hospital has nine people in a serious condition, while a third facility has three people in intensive care who suffered severe burns.

The drummer and bassist of the band on stage are among those seriously hurt, it has been reported.

One woman inside the club told Romanian TV there was fire "all over the place", adding: "I saw people changing their mood from happiness to deep panic."

60 ambulances and fire engines were at the scene, and some victims were being resuscitated on the street outside.

An Interior Ministry spokesman has warned the death toll is likely to rise, and many victims are yet to be identified.

"We have many people with burns, intoxicated with smoke and people squashed," Raed Arafat added.

One eyewitness said there was a stampede of people running out of the club after the fire, in one of Bucharest's worst incidents for decades.

Another added: "People were fainting from the smoke. It was total chaos, people were trampling on each other."

The country's president, Klaus Iohannis, has expressed his "complete sympathy and solidarity with the families of those affected".

Prime Minister Victor Ponta is cutting short a visit to Mexico and flying home in light of the tragedy.

An investigation into the incident has begun, and an emergency meeting of cabinet ministers is taking place this morning.

The owner of the nightclub is helping police with their inquiries.

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