This is the heart-stopping moment a cargo barge almost smashed into a historic fort when its tether snapped.

The vessel was being towed by a motorboat when it was caught in a powerful current on the Chao Phraya River in Ayutthaya, Thailand.

Footage shows how the barge drifted toward the centuries-old Pom Phet Fort, stopping just short of hitting a platform as locals yelled in alarm.

The boat operator, in a last-minute save, managed to secure the tether and revved the engine, successfully tugging the barge back into control.

Peerathorn Naksuk, Director of the Ayutthaya Regional Harbour Office, said: 'The boat operator is experienced, but he still misjudged the situation. He probably thought that because the barge was light, that it could be towed against the current easily.

'But this year, unusual currents are affecting the Chao Phraya River near Wat Phanan Choeng temple, creating whirlpools different from previous years. We still don't understand. Boat operators must carefully assess their engine power or accidents can occur.'

Pom Phet Fort is a 16th-century fortress in Ayutthaya, built at the confluence of the Chao Phraya and Pa Sak rivers. The historic site, one of two surviving fortresses in the province, now serves as a public park and tourist attraction.