Dramatic footage shows flames engulfing a school bus - burning alive up to 25 pupils in Thailand this morning.

The coach was carrying pupils from the Wat Khao Phraya Sangkharam School in Uthai Thani province to an electricity plant for an educational visit when a wheel exploded in Pathum Thani province on the outskirts of Bangkok at around 12:38 pm local time.

A fire is said to have started in the undercarriage as the vehicle hit the concrete road barriers. Dramatic footage shows the blaze engulfing the entire vehicle before firefighters arrived to put out the inferno.

Officials said that up to 25 children were killed when they were burned alive as they scrambled to escape. They said they were in Grade 3, making them around nine years old. Others, including teachers, were able to escape.

Pictures from the scene showed their charred corpses in the burned-out vehicle. Firemen took some of the children who were able to escape the blaze into a nearby building, where they were seen being counted.

Politicians visited the scene of the wreckage to express their condolences.

Speaking on the roadside, one teacher said: ‘We are from Wat Khao Phraya Sangkharam School in Uthai Thani with three buses.

‘The incident occurred on the second bus.'

A driver of one of the school vehicles in the convoy told local media that he saw the front wheel of the bus explode before flames appeared.

A witness said they heard an explosion before seeing the bus travelling at high speed, followed by an accident with a burst of flames and smoke.

Another witness said that officers were hesitant to approach the scene while the bus was burning, prompting students to huddle together inside the vehicle.

The owner of the rented coaches from the Chinnaboot Tour company said that his buses picked up students at their school in Uthai Thani before travelling to the head office of the Electricity Generating Authority of Thailand for a school trip.