China's air force has revealed that a new type of tanker aircraft conducted refueling operations during a joint aerial patrol with Russia in May.

People's Liberation Army Air Force officials told reporters that the YU-20 aerial tanker was deployed to the patrol over the Sea of Japan and the East China Sea to refuel Chinese J-16 fighter jets.

Officials had not previously disclosed the participation of YU-20 in the May joint mission, which also featured H-6K bomber craft.

The air force also released footage of an in-flight refueling operation. But it is unclear when and where it was filmed.

China's state-run Xinhua news agency reports that the YU-20 is a next-generation tanker aircraft and will help reinforce the air force's ability to launch long-range operations.

Ohara Bonji, a senior researcher at the Sasakawa Peace Foundation, said that, with the help of refueling aircraft, Chinese warplanes will be able to fly a longer distance and conduct operations across wider areas.

The former Japanese Maritime Self-Defense Force official warned that the development could pose a threat not only to Taiwan, but also to Japan and other Asian countries.