This is the terrifying moment visitors were left dangling in mid-air for more than 20 minutes when a roller coaster broke down.

The Vortex ride at the Siam Amazing Park in Bangkok, Thailand, malfunctioned, leaving stunned riders stranded high above the ground on October 23.

Footage shows the suspended roller coaster motionless while passengers were trapped in their seats.

Staff were seen briefing the riders shortly before a rescue team arrived to help them. There were no injuries reported.

Onlooker Kageemas Tanachattra said: 'I was with my family, including my son.

‘While waiting in the queue, I noticed that it was taking unusually long, and there were no screams from the riders.

‘I spoke with the others, wondering why it was delayed, until I saw an employee checking the chain and talking on a walkie-talkie. That's when I realised the ride might have malfunctioned.

‘I felt very lucky that I was not among those stuck on the ride.

‘Employees arrived quite quickly, and people were brought down from the ride around 5 pm.

‘After the incident, I went to another ride, which also malfunctioned, but it didn't need to be stopped.

‘I had already paid for a ticket that covered all rides, but I'm not sure whether those stuck on the ride received any refund or compensation.'

A fairground employee said the glitch may have been caused by an electrical system failure, which stopped the chain that moves the ride.

Managers reassured visitors that the coaster's design allows it to descend safely by gravity across inversions if such a failure occurs.

Vortex is a suspended roller coaster at the Siam Amazing Park in Bangkok, measuring 0.5 miles (765 metres) in length and featuring five inversions.