Six people were killed and 14 injured in a gas explosion caused by a vehicle crash in Mongolia's capital on Wednesday, authorities said.

A truck carrying 60 tons of liquified natural gas (LNG) collided with a car and exploded in the early hours, the Mongolian National Emergency Management Agency (NEMA) said on its website.

"According to preliminary results, three people died in the fire," NEMA said on its website, adding three firefighters had also been killed while 14 people had been sent for medical treatment.

Ten of those were taken for treatment for burns, while one child was being treated for poisoning and three other infants were being cared for.

Rescue teams were dispatched to the scene and the fire had been extinguished, it added.

Images shared by NEMA showed emergency services at the scene of the fire early morning as huge flames engulfed the street.

Pictures also showed the burnt-out husks of two vehicles and widespread damage to the street, with windows blown out at a nearby school.

An AFP journalist on the scene saw the remains of the truck, with little left but twisted metal.

Residents of a nearby apartment block had been temporarily relocated, NEMA said, adding roads around the area were closed as authorities worked to clean up debris.

US Ambassador to Mongolia Richard Buangan said he was "deeply saddened to learn of the tragic accident".

"I would like to extend my heartfelt condolences to the families and colleagues of the NEMA staff members who lost their lives in this devastating event," he said in a post on social media platform X.

The EU's ambassador to Mongolia, Axelle Nicaise, also said she was "shocked and devastated" by the accident.