Polish tourists fled to safety as a bus taking them to Ayutthaya burst into flames and was destroyed on an expressway in Bangkok on Wednesday morning.

The bus was carrying 15 tourists from Poland and their Thai guide. There were no injuries reported, but many passengers lost their luggage to the fire.

The bus burst into flames while outbound on the Si Rat Expressway, above the central bus terminal, about 7.55am, according to traffic radio FM91 Trafficpro.

Fire trucks and crews took about 20 minutes to put out the fire. By then the bus was totally gutted.

The fire caused heavy traffic congestion in the area.

The bus driver said that while outbound on the expressway, he saw smoke coming from a luggage compartment, and there was the smell of something burning.

He immediately parked the bus on the left side of the expressway and got out to check. All passengers were asked to also leave the vehicle.

The driver said he managed to remove some passengers' bags from the bus before it burst into flames and he was forced to retreat.

The bus was totally destroyed.