BEIJING • China's flight to a newly built airfield on Yongshu Reef, also known as Fiery Cross Reef, on the Nansha Islands is a matter "completely within China's sovereignty", the country's Ministry of Foreign Affairs said in a statement in response to an official protest from Vietnam, which said the flight "undermines peace and stability".
China will not accept Vietnam's "unfounded accusations" and hopes Vietnam can work towards achieving "sustainable, healthy and stable" development of bilateral ties, ministry spokesman Hua Chunying said in its statement last Saturday, referring to the Spratly Islands by their Chinese name.
She added that China had used a civil aircraft to conduct the flight to test whether the airfield facilities meet civil aviation standards.
Vietnam said in a statement on its government website that China's flight to the disputed islands damages "political trust" and ties between the nations, and "goes against the common perceptions of the senior leaders of the two countries".
China's flight to the airfield "encroaches on Vietnam's sovereignty", Foreign Ministry spokesman Le Hai Binh said in the statement.
Vietnam handed a protest note to China's embassy last Saturday and asked China not to repeat the action, according to Mr Binh.
It called the flight "a serious infringement of the sovereignty of Vietnam on the Spratly archipelago".
The United States said it was concerned that the flight had exacerbated tensions. State Department spokesman Pooja Jhunjhunwala said there was "a pressing need for claimants to publicly commit to a reciprocal halt to further land reclamation, construction of new facilities, and militarisation of disputed features".
The controversy comes just several days after China's Defence Ministry announced that it had launched a direct phone link with Vietnam.
Last Thursday, Chinese Defence Minister Chang Wanquan had his first phone conversation with his Vietnamese counterpart Phung Quang Thanh.
The two 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.
China has been building islands in the South China Sea on reclaimed reefs as it tries to beef up its presence in the area. Late last year, it completed an airfield on Fiery Cross Reef that security experts say could accommodate most Chinese military aircraft.
Yesterday, more trouble was brewing after four vessels operated by China's coast guard reportedly entered waters around the disputed Senkaku, or Diaoyutai, Islands,
The Okinawa-based 11th Regional Coast Guard Headquarters of Japan said its vessel warned the approaching Chinese ships not to move closer to Japan's waters, Kyodo news agency reported. Chinese coast guard ships were last seen in the area on Dec 26, according to Kyodo. Japan, China and Taiwan have competing claims to the Senkaku Islands.