TAIPEI (Reuters) – A U.S. warship sailed through the sensitive Taiwan Strait on Thursday, the U.S. and Taiwanese militaries said, on the same day as the 31st anniversary of China’s bloody crackdown on pro-democracy demonstrators in and around Tiananmen Square.

China, which considers Taiwan its territory, has been angered by the Trump administration’s stepped-up support for the self-ruled, democratic island, such as more arms sales and nearby U.S. patrols.

Taiwan’s Defence Ministry said on Friday the U.S. warship had transited the narrow Taiwan Strait that separates the island from the mainland, heading south.

Taiwan’s armed forces monitored the ship, which it described as being on an “ordinary mission”, the ministry added, without providing further details.

The U.S. Pacific Fleet, in a post on its Facebook page, named the ship as the USS Russell, an Arleigh Burke-class destroyer.

The United States has in recent months stepped up its sailings through the Taiwan Strait, to China’s anger, adding to tensions over everything from Beijing’s response to the coronavirus pandemic to trade and human rights.

Public events took place in both Taiwan and Chinese-ruled Hong Kong on Thursday to mark the 1989 Tiananmen anniversary.

Police pepper-sprayed some Hong Kong protesters on Thursday who defied a ban to stage candlelight rallies in memory of the crackdown, accusing Beijing of stifling their freedoms too.