HANOI • Vietnam yesterday formally accused China of violating its sovereignty and a recent confidence-building pact by landing a plane on an airstrip that Beijing has built in a contested part of the South China Sea.
Foreign Ministry spokesman Le Hai Binh said China had conducted a test flight to the airfield, "built illegally on Fiery Cross Reef, which is part of Vietnam's Spratlys".
In a statement, he called it "a serious infringement of the sovereignty of Vietnam on the Spratly archipelago, contrary to the common perception of high-ranking leaders of the two countries and (to) an agreement on the basic principles for directly solving maritime issues between Vietnam and China".
Vietnam handed a protest note to China's embassy and asked China not to repeat the action, Mr Binh said.
The protest came two days after China's Defence Ministry announced it had launched a direct phone link with Vietnam.
On Thursday, Chinese Defence Minister Chang Wanquan had his first phone conversation with his Vietnamese counterpart Phung Quang Thanh.
During the call, Mr Chang said China-Vietnam relations continued to improve last year as top leaders of the two countries successfully exchanged visits.
It is in accordance with the interests of China and Vietnam to enhance and deepen defence cooperation, Mr Chang said.
Mr Thanh spoke highly of the progress made on developing bilateral military ties, adding that Vietnam is ready to forge ahead the ties in the new year so as to benefit both countries, Xinhua news agency reported.
The two communist-led states' competing claims in the South China Sea came to a head in 2014 when Beijing parked an oil rig off the Vietnamese coast, leading to anti-China riots.
Late last year, China completed an airfield on Fiery Cross Reef that security experts say could accommodate most Chinese military aircraft.
Chinese President Xi Jinping visited Hanoi in November at a time of uncertainty over what kind of leader will emerge from this month's five-yearly Congress of the Vietnamese Communist Party, traditionally close to Beijing but now getting intense Western attention, especially from the United States.
Both sides agreed during Mr Xi's visit to maintain peace in the sea and build a relationship of trust.
China claims almost all of the South China Sea, which is believed to have huge deposits of oil and gas, and through which about US$5 trillion (S$7.1 trillion) in ship-borne trade passes every year.
It has been building up military facilities on the islands it controls.
Brunei, Malaysia, the Philippines and Taiwan also have claims in the South China Sea.