KINMEN, (Taiwan): Amid rising tensions with Beijing, the de facto US ambassador in Chinese-claimed Taiwan took part on Sunday for the first time in commemorations of a key military clash and the last time Taiwanese forces joined battle with China on a large scale.

China has stepped up military activity around the democratic island, moves denounced by Taiwan's government as an attempt at intimidation to force them to accept Chinese rule.

Taiwan President Tsai Ing-wen laid a wreath and bowed her head in respect at a memorial park on Kinmen island, which sits a few kilometres (miles) off the Chinese metropolis of Xiamen, to mark the 62nd anniversary of the start of the second Taiwan Straits crisis.

In August 1958, Chinese forces began more than a month of bombarding Kinmen, along with the Taiwan-controlled Matsu archipelago further up the coast, including naval and air battles, seeking to force them into submission.

Brent Christensen, head of the American Institute in Taiwan and Washington's de facto representative, offered his respects too, standing behind Tsai, in a symbolic show of US support for the island.

Christensen also laid wreaths at a monument honouring two US military officers who died in a 1954 Chinese attack on Kinmen, the institute said.

"Commemorations such as these remind us that today's US-Taiwan security cooperation builds on a long and proud history that exemplifies the phrase 'Real Friends, Real Progress," it said in a statement.

Taiwan's presidential office thanked Christensen for participating on a day it said serves to remind Taiwan's people of the importance of defending freedom and democracy.

China's Taiwan affairs office did not immediately respond to a faxed request for comment on the commemoration.

Washington has no formal ties with Taipei but is its largest arms supplier. President Donald Trump's administration has made bolstering relations a priority, to Beijing's anger.

Like Tsai, Christensen did not make public comments.

Taiwan fought back at the time with support from the United States, which sent military equipment like advanced Sidewinder anti-aircraft missiles, giving Taiwan a technological edge. The crisis ended in a stalemate.

Major General Liu Qiang-hua, spokesman for the Kinmen Defence Command, said it was important to remember an event that was crucial to ensuring Taiwan's security.