That's according to Mongolia's officials.

They added that around a dozen people were injured by the fire near the Dunjingarav market.

More than 600 firefighters in 100 vehicles were involved in putting the fire out, which was eventually extinguished.

And Mongolia's Emergency Management Office confirmed on Facebook that three National Fire Service officers were killed.

According to Mongolia's deputy prime minister, preliminary assessments showed that the truck crashed into a small car causing an immediate explosion.

Then a second blast occurred, ripping off a part of the truck with great force and killing the firefighters at the scene.

According to local online news outlets and eyewitness footage, the fire quickly engulfed several nearby buildings, including a residential building. Scores of cars were burnt.

Residents told television channel TenGer TV that a group of them had to forcibly break out of the building after flames reached the communal exit.

The deputy prime minister said there were no casualties reported from the apartment building, but could not "guarantee that the casualty count will not increase" as investigation and emergency measures were still underway.