BANGKOK: An explosive fire at a popular bar in Thailand's capital Bangkok has killed 27 people, the country's prime minister and other officials said on Monday (Jul 13), in one of the deadliest such incidents in the tourism hub in recent years.

An AFP journalist saw several black body bags on the ground outside the Rong Beer Na Lat Phrao bar and restaurant early Monday morning, while dozens of emergency service workers thronged the scene.

Numbered bodies lay in two rows awaiting removal, surrounded by a large number of rescue workers. Firefighters stood near the bar's entrance, its facade scorched and blackened by the blaze.

"The fire spread very quickly, reaching up to the ceiling. Smoke was likely the main cause of death," Bangkok Governor Chadchart Sittipunt told reporters outside the venue on the outskirts of the Thai capital.

He said 27 people were killed and 63 were hospitalised with injuries, including 22 in critical condition, adding that authorities had launched an investigation.

A number of the victims were found near the fire exit and authorities believe there may have been obstructions blocking it, he said.

"I heard loud screaming from a lot of people inside - chaos happened," Laotian tourist Kan Kutirat told AFP.

He shared a video on Facebook, verified by AFP, that showed patrons - several with their shirts ablaze - fleeing into the street as flames surged out the door.

Kan said he was drinking alone at the bar at around 10pm on Sunday when he noticed smoke rising near the stage.

"I never experienced anything like this before," he said. "The images are still stuck in my mind."

He said he helped carry a woman out of the bar.

On his post, he added: "I could only get one person out. I tried my best. I'm sorry."

SMOKE, THEN AN EXPLOSION AND FIRE

Firefighter Chakrit Khongkom, 45, said he arrived on the first fire truck to see the Rong Beer Na Lat Phrao pub alight and many patrons stranded inside, several of them trying to escape from the back of the venue. 

The few people coming through the front of the venue were burnt.

"The fire was not that aggressive, but the smoke had engulfed 100 per cent of the venue. The smoke was everywhere," he said. 

"Most of the survivors were choking on smoke." 

Body-camera footage from an emergency worker seen by Reuters showed firefighters in oxygen masks moving through the darkened remains of the pub with torches as they searched for survivors.

Several victims can be seen lying prone on the floor near the pub's toilets while rescue workers carry in stretchers.

The video also shows what appears to be the fire-damaged main room of the venue, with bar tables and stools still visible.

Chadchart said the pub had procured proper permits and had fire exits, but the fire spread rapidly and smoke filled the room, potentially making it hard for patrons to escape.

In the early hours of the morning, emergency personnel remained at the scene as bodies were prepared for transport and forensic teams collected evidence to help identify the victims.

Numbered bodies lay in two rows awaiting removal, surrounded by a large number of rescue workers. Firefighters stood near the pub's entrance, its facade scorched and blackened by the blaze.

A band member at the venue told local media that smoke suddenly filled the room after the lights briefly went out, followed by a massive explosion and fire.

"After the explosion I didn't see anybody trying to run, most of them were on the floor asking for help," he told reporters, his head still bandaged, without giving his name.

"I ran towards the door from the stage, about five metres. It was dark and there was smoke, no oxygen."