The unannounced two-day trip by senior members of Congress prompted China to renew its rhetoric that it would "prepare for war" over Taiwan.

The five-strong delegation - led by senator Ed Markey of Massachusetts - met with President Tsai Ing-wen, according to Washington's de facto embassy.

Tsai told the lawmakers she wants "to maintain a stable status quo across the Taiwan Strait" and "jointly maintain the prosperity and stability of the Indo-Pacific region," her office said.

She said Russia's invasion of Ukraine demonstrated "the threat that authoritarian states pose to the world order."

A spokesman said the defense ministry had carried out a fresh round of "combat readiness patrol and combat drills in the sea and airspace around Taiwan island."

"We warn US and the DPP authorities: 'Using Taiwan to contain China' is doomed to failure," he added, referring to Taiwan's ruling Democratic Progressive Party.

Taiwan's defense ministry vowed to face the latest drills "calmly and seriously and defend national security."

Its forces detected 30 mainland planes and five ships operating around the strait. Of those, 15 planes crossed the median line - an unofficial demarcation that Beijing does not recognize.

The drills followed days of huge exercises around Taiwan in the wake of Pelosi's visit, which saw Beijing send warships, missiles and jets into the waters and skies near the island.

Taipei condemned those drills and missile tests as preparation for an invasion.

Taiwan has also seen a flurry of delegations visit from Europe and other Western allies in recent years, partly in response to Beijing's more aggressive stance under President Xi Jinping.