Six people, including three firefighters, died in Ulaanbaatar after a fuel tanker truck carrying 60 tonnes of liquefied natural gas (LNG) crashed and exploded in a fireball on a city street at around 01:00 (local time) on January 24.

The explosion in the Mongolian capital occurred after a collision with a small car at a roundabout, officials said. Six hundred firefighters were sent to battle the blaze. At least 11 people were injured as the fire spread to nearby buildings and scores of cars were burnt. Shocked city dwellers are now asking why a tanker carrying dangerous fuel was permitted to travel into the residential neighbourhood, containing many schools.

One local resident told Reuters how he initially thought that a plane had crashed. Erdenebold Sukhbaatar, a 40-year-old lawyer who livestreamed events on Facebook, said the crash felt like an earthquake, but was followed by a bright light.

"It was very strong. And then I've never seen such kind of, like, strong [explosion]. It was like 60, you know, tonnes [of LNG on the truck], which means 60,000, litres [of gas] you know. It was like huge liquid gas," Erdenebold was quoted as saying.

"You know, if it happened [in] the daylight time, especially during the rush hours in the morning or in the evening, [it would] be more harmful," he added.

"This shows city planning is really bad," another local resident, Ankhbayar Galbadrakh, told AFP. "All of these trucks—with gas or without gas—should travel outside of the city limit."

Another city inhabitant told TenGer TV how the force of the explosion not only blew out their windows, it also destroyed their balcony.

Sainbuyan Amarsaikhan, Mongolia's deputy prime minister, said the firefighters died in a secondary explosion that threw a section of the truck "with a lot of force", resulting in the "tragic loss" of life.

The Mongolian National Emergency Management Agency (NEMA) said that four children were among the injured, including one who was being treated for poisoning.