China’s air force has landed long-range military aircraft on an island in the disputed South China Sea, a move that is believed to be the first of its kind and is likely to fuel further concerns about Beijing’s intentions in the region.

China Daily published a video purporting to show takeoff and landing of military planes, including the long-range, nuclear strike capable H-6K , in the diplomatically charged region on Friday.

Beijing is pitted against smaller neighbors in multiple disputes in the South China Sea over islands, coral reefs and lagoons in waters crucial for global trade and rich in fish and potential oil and gas reserves.

It has begun building military structures on disputed islands – much to the dismay of other South-East Asian nations including the Philippines, Indonesia, Malaysia, Taiwan and Vietnam.

Late on Friday, a statement from China‘s defence ministry said the exercise was conducted on an island reef in a “southern sea area”, without specifying the exact location of the site.

Wang Mingliang, a defence expert cited in the statement, said the exercises on islands in the South China Sea were aimed at helping the air force “strengthen its combat capability to deal with maritime security threats.”

Using Chinese social media posts, the Washington-based Asia Maritime Transparency initiative identified the location as Woody Island, China’s largest base in the Paracel Islands.

The United States criticised the move and vowed to continue working to insure that the Indo-Pacific region remain “free and open”.

“We have seen these same reports and China’s continued militarisation of disputed features in the South China Sea only serves to raise tensions and destabilise the region,” Lieutenant Colonel Christopher Logal was quoted as saying by The Associated Press on Saturday.

The US and regional allies accuse China of militarising the region as part of its efforts to lay claim to the contested territory.

Chinese infrastructure in the disputed islands includes airbases, radar and communications systems, naval docks and landing strips to accommodate military planes.