China claims self-ruled Taiwan as part of its territory and has said it will never renounce the use of force to bring the island under its control.

Beijing has upped military and political pressure on Taiwan in recent years, and conducted military drills in May around the island days after the inauguration of Taiwanese President Lai Ching-te.

"Taiwan is not the only target of PRC efforts to use intimidation and coercion to change the status quo," said Raymond Greene, director of the American Institute in Taiwan (AIT), the de facto US embassy, using the acronym for China's official name.

"More and more countries are realising the importance of cooperating with the United States and other like-minded partners to preserve the rules-based international system," Greene said during his first news conference as AIT director.

US efforts to build alliances in the region "are not meant to prepare for war but to prevent it", he added.

China's campaign of confrontation has also extended to remote reefs in Southeast Asia and far-flung Japanese islands.

Beijing has deployed military and coast guard vessels to press its claims to almost the entire South China Sea, despite an international ruling that its assertion has no legal basis.

Taiwan -- separated from China by the narrow 180-kilometre (110-mile) Taiwan Strait -- has its own government, military and currency.

To press its claims, Beijing maintains a near-daily military presence, sending in fighter jets, drones and naval vessels around Taiwan.

The island's defence ministry announced Wednesday night that it had detected military activity in China's Fujian province across the Taiwan Strait.

"Since yesterday, various types of PLA aircraft, helicopters, and drones have been detected, along with amphibious ships and roll-on/roll-off cargo vessels loading ground forces, conducting joint landing drills near Dacheng Bay," the ministry said, referring to China's military.

It added that the ministry has "monitored the situation".

As China has increased pressures around the island, Taiwan has sought to strengthen ties with friendly countries while ramping up military purchases from the United States, its key ally.

Washington switched diplomatic recognition from Taipei to Beijing in 1979 but has remained Taiwan's biggest arms supplier, sparking repeated condemnations from China.

Greene also said Wednesday that the United States would not "rule out" weapons co-production with Taiwan in the future.