BEIJING (AP): Chinese military forces are holding exercises near Taiwan in response to a visit by a U.S. congressional delegation to the island.

The drills in the area of the Taiwan Strait are a necessary measure to safeguard national sovereignty," China's Defence Ministry said in the announcement Tuesday that gave no details on the timing, participants and location of the exercises.

It said the joint war preparedness patrol by the Eastern Theatre Command was prompted by the seriously incorrect words and actions of relevant countries over the issue of Taiwan and the actions of those advocating the self-governing island's independence.

The U.S. has strong but informal relations with Taiwan, and tensions have been rising between the U.S. and China over several issues including Hong Kong, the South China Sea, the coronavirus pandemic and trade. Details on the U.S. delegation that reportedly arrived in Taiwan on Tuesday were not immediately available.

A Chinese Defence Ministry statement from an unidentified spokesperson strongly condemned the visit, saying no one should underestimate the firm determination of the People's Liberation Army to safeguard the Chinese people's national sovereignty and territorial integrity.

China regards Taiwan as its own territory to be annexed by military force if necessary. The sides split amid civil war in 1949 and, following a brief period of rapprochement, relations have grown increasingly tense under Taiwan's independence-leaning President Tsai Ing-wen.

During China's National Day weekend in early October, China dispatched 149 military aircraft southwest of Taiwan in strike group formations, causing Taiwan to scramble aircraft and activate its air defence missile systems. Taiwan's Defence Ministry said this week such tactics were aimed at wearing down the island's defences and degrading morale.

In Washington, Pentagon spokesperson John Kirby said congressional visits to Taiwan are relatively common and in keeping with U.S. obligations under the Taiwan Relations Act," which obligates the U.S. government to ensure Taiwan has the ability to defend itself and regard threats to the island as matters of grave concern."

The delegation arrived in Taipei on Tuesday evening aboard a C-40 Clipper jet, which departed soon afterward, according to Taiwan's official Central News Agency. Kirby said travelling on a U.S. military jet was customary for such delegations.

Details of the members of the delegation and how long they planned to stay on the island were not immediately available.

Taiwanese Foreign Ministry spokesperson Joanne Ou said ministry had worked with the American Institute in Taiwan, which is the de facto U.S. Embassy, on arrangements for the visit but gave no details. She said further information would be released at the appropriate time.

Although the U.S. switched diplomatic ties from Taipei to Beijing in 1979, it retains strong informal political and military relations with Taiwan. As a vibrant democracy, Taiwan also enjoys strong bipartisan support in Congress and the U.S. government has been boosting relations through high-level visits and military sales.

That has been a key source of friction with Beijing amid a string of disputes over trade, technology, human rights and other issues.