Man claims to be first person to pilot balloon into underground cave

An Austrian balloon pilot has defied the laws of gravity by piloting a hot-air balloon into an underground cave.

Ivan Trifonov, 70, managed to descend into Mamet Cave, on Velebit Mountain in Croatia, a feat which he believes is a world first.

The stunt was captured on multiple cameras, including one inside the balloon, which shows Mr Trifonov carefully navigating the tight space around him.

And with the cave a tight 60 metres wide and 206 metres deep, there was no room for error.

"It was very hard and I don’t think anyone else will ever repeat this venture," Mr Trifonov told AAP.

Mr Trifonov will now submit the video to the Guinness Book of World Records.