Researchers test China's AUV "Wukong". (Photo provided to China News Service)

China's Wukong, a fully autonomous submersible developed by Harbin Engineering University, has reached a maximum underwater depth of 7,709 meters, setting a new record for domestic autonomous underwater vehicles.

Wukong returned to its home port of Qingdao, Shandong Province on Thursday after completing the third phase of its deep-sea trial.

This photo shows sediment collected by fully autonomous submersible "Wukong" at 7,705 meters in the sea. (Photo provided to China News Service)

During this year's deep-sea scientific expedition in the Western Pacific Ocean organized by the National Deep Sea Center of China from February 24 to April 1, WuKong had successfully reached a maximum deep-sea diving depth record of 7,709 meters, breaking its previous record of 5,213 meters.

Capable of full-ocean depth, it dived 5,000 meters and 7,000 meters respectively during the sea trials and retrieved in-situ water samples, laying a solid foundation for 11,000-meter submersible tests.

This is the second deepest record in the world after the one set by the Russian Vityaz-D AUV.

Wukong, 2 meters long, 1 meter wide and 1.3 tons in weight, completed two sea trials at a 1,500-meter depth in 2019.

Researchers from Harbin Engineering University's key technology research project team for full-ocean depth autonomous underwater vehicle (AUV). (Photo provided to China News Service)