Taiwan said Wednesday that China had positioned anti-aircraft missiles on a disputed South China Sea island claimed also by Taiwan and Vietnam and watched closely by Washington.
Taiwan's Ministry of National Defense said in a statement it had "grasped that Communist China had deployed" an unspecified number of missiles on Woody Island in the Paracel group.
The move would follow China's efforts to build new islands in the disputed sea by piling sand atop reefs and then adding airstrips and military installations. The most dramatic work has taken place in the Spratly Island group, where the militaries of four nations have a presence, although similar work has also gone on at Woody and other Chinese holdings in the Paracels.
"The military will pay close attention to subsequent developments," the ministry's statement said. Relevant parties should "work together to maintain peace and stability in the South China Sea region to refrain from any unilateral measure that would increase tensions," the statement added.
U.S. network Fox News also said China had moved surface-to-air missiles to the Paracels, identifying them as two batteries of a system known as HQ-9, along with radar targeting arrays. The missiles have a range of about 200 kilometers (125 miles), making them a threat to all forms of civilian and military aircraft.
Taiwan and China claim almost the whole 3.5 million-square-kilometer (1.35 million-square-mile) South China Sea, including the Paracel chain. Vietnam and the Philippines claim much of the ocean, as well. Brunei and Malaysia have smaller claims.
Home to some of the world's busiest sea lanes, the ocean is also rich in fisheries and may hold oil and natural gas reserves under the seabed.
China's move is likely to rattle Vietnam the most because of its proximity to the Paracels and because of a history of maritime tensions with China that culminated in 2014 with a standoff after China moved a massive oil rig into disputed waters.
China's moves to assert its sovereignty claims in the South China Sea are expected to be discussed during a visit by Australian Foreign Minister Julie Bishop to Beijing on Wednesday.
In an interview Monday on Japanese TV, Bishop said Australia called on all parties to cease construction work and militarization of the islands.
Chinese Foreign Ministry spokesman Hong Lei responded by saying Australia should adopt an "objective and unbiased attitude" toward South China Sea matters.