Beijing/Taipei, October 20 (Reuters) — China's military said on Tuesday it had sent forces to watch a US warship that it said 'illegally' entered waters around a disputed shoal in the South China Sea, while further north in the waterway, Taiwan reported a standoff with a Chinese ship.

The Chinese military's Southern Theatre Command said the USS Charleston 'illegally intruded' into waters adjacent to Sabina Shoal in the Spratly Islands without Chinese government approval in the early hours of Tuesday. 'The US action infringes upon China's sovereign rights and interests, jeopardizes maritime security, and is detrimental to regional peace and stability,' it said in a statement. 'The US side should immediately cease such activities.' China's navy dispatched forces to track and monitor the ship, it added. The US Navy did not immediately respond to a request for comment; it generally refers to such missions as 'freedom of navigation operations', though its last known one in the South China Sea was more than a year ago. A Philippines military spokesperson said the US ship 'did not trespass into Chinese territory', adding that no nation had the authority to require prior permission for 'lawful transit through international waters'.

China views almost all of the busy South China Sea as its own territory, despite overlapping claims by Brunei, Malaysia, the Philippines, Taiwan and Vietnam, with recent tension most pronounced between Beijing and Manila. China and the Philippines, which has a mutual defence treaty with the US, both contest sovereignty over Sabina Shoal and the entire Spratly Islands archipelago. Last month, a China Coast Guard vessel rammed a Philippine boat on a refuelling mission near the same shoal, according to the Philippine Coast Guard; China blamed the collision on the Philippine side.

In a separate incident on Tuesday at the top end of the South China Sea, Taiwan's Coast Guard said a Chinese Coast Guard ship had entered restricted waters near the Taiwan-controlled Pratas Islands. Taiwan's Coast Guard said its ship the 'Taichung' was dispatched to warn away the Chinese boat, while both sides broadcast messages to each other. The Chinese ship broadcast that 'the so-called Republic of China does not exist', referring to Taiwan's official name, while the Taiwanese ship broadcast back that 'the Republic of China, Taiwan, is a sovereign and independent country', Taiwan's Coast Guard said, adding the standoff was continuing. China's Taiwan Affairs Office did not immediately respond to a request for comment. The office said last week that Taiwan must 'bear the consequences' of its Coast Guard using a water cannon against a Chinese fishing boat near the Pratas. The Pratas Islands lie roughly between southern Taiwan and Hong Kong, but are only lightly defended and security is the responsibility of Taiwan's Coast Guard.

Sources: Reuters reporting by Liz Lee and Ben Blanchard; Southern Theatre Command statement; Taiwan Coast Guard statement; Philippines military spokesperson as reported by Reuters.