China's state-of-the-art Jiaolong submersible has broken the country's deep-sea dive record, plunging more than 6,000 metres below the surface of the Pacific.

Three divers clambered on board the ship before it was craned off mother ship Xiangyanghong 09, and dived into the Ocean's Mariana Trench on Friday.

In eight hours, the crew reached 6,379 metres - some way short of the Ocean's lowest point, Challenger Deep, but still an impressive achievement.

The dive is one of a series of ever-deeper descents, aiming to break the 7,000 metre mark.