Beijing - An American warship on Sunday sailed close to a disputed island in the South China Sea occupied by Beijing, as part of an operation to demonstrate freedom of navigation in the waters, a US official said.

The destroyer USS Stethem passed less than 12 nautical miles (22 kilometers) from tiny Triton Island in the Paracel Islands archipelago, which is also claimed by Taiwan and Vietnam, the official told AFP.

The operation, which is likely to provoke Beijing, is the second of its kind carried out by the United States since President Donald Trump took office.

The first was on May 25, when the USS Dewey, a guided-missile destroyer, sailed less than 12 nautical miles from Mischief Reef - part of the disputed Spratly Islands south of the Paracel Islands.

China claims nearly all of the South China Sea, despite partial counter-claims from Taiwan and several southeast Asian nations including the Philippines, Brunei, Malaysia and Vietnam.

The United Nations says countries can establish the reach of their territorial waters up to a limit of 12 nautical miles.

China has rapidly built reefs into artificial islands capable of hosting military planes. Freedom of navigation operations are designed to challenge the sovereignty of countries with claims to disputed territory. Washington has challenged annexations of South China Sea islets while advocating for a diplomatic settlement.

China has recently built up its facilities on Triton Island, including a new helicopter landing site, according to the Asia Maritime Transparency Initiative, part of the Center for Strategic and International Studies think tank.

A large Chinese flag is displayed on the island, visible from aerial and satellite photos.

According to the Pentagon, the United States in fiscal year 2016 conducted freedom of navigation operations "challenging excessive maritime claims of 22 different coastal states, including claims of allies and partners."

US-Chinese relations were already strained last week when Trump authorized a new arms sale to Taiwan, which China considers a rebel province, and when the US slapped sanctions on a Chinese bank accused of laundering North Korean cash.

Meanwhile, Taiwan military jets scrambled to shadow a Chinese aircraft carrier passing through narrow waters separating the two sides en route to Hong Kong to mark the 20th anniversary of the former British colony's return to China.

The Liaoning fleet will be open to the public in Hong Kong and showcase the "military might" of the Chinese naval force, Xinhua citied Yang Liang, China's People's Liberation Army Navy spokesman, as saying.

It is due to arrive on Friday, Hong Kong media said.

Chinese President Xi Jinping swore in Hong Kong's new leader on Saturday with a stark warning that Beijing will not tolerate any challenge to its authority in the divided city, in his strongest speech yet amid concerns over what some perceive as increased meddling by Beijing.

The Soviet-built Liaoning, whose home port is in northern China, entered Taiwan's air defence identification zone (ADIZ) on Saturday and was sailing just west of the middle of the Taiwan Strait on Sunday, Taiwan's defence ministry said in a statement.

Taiwan military jets and ships were deployed in response to monitor the fleet's passage, the ministry said.

Nothing abnormal had been detected as the Chinese battle group headed southwest and was expected to leave Taiwan's ADIZ by Sunday evening, the ministry said.

It was the third time that the Liaoning has sailed near self-ruled Taiwan, which China claims as its own, in recent months for what Beijing has said were routine drills in December and again in January.

China has never renounced the use of force to bring Taiwan under its control.