Taiwan blasted its "evil neighbour next door" today after China encircled the island with a series of huge military drills that were condemned by the United States and other Western allies.

The jets were to warn away 49 Chinese aircraft in its air defence zone, the Taiwanese Defence Ministry said, after they crossed the Taiwan Strait median line, a statement said.

During yesterday's military exercises, which continued today, China fired ballistic missiles and deployed both fighter jets and warships around Taiwan.

The People's Liberation Army declared multiple no-go danger zones around Taiwan, straddling some of the busiest shipping lanes in the world and at some points coming within 20km of the island's shores.

Beijing has said the exercises will continue until midday Sunday, and Taipei reported that Chinese fighter jets and ships crossed the "median line" that runs down the Taiwan Strait this morning.

"As of 11am, multiple batches of Chinese warplanes and warships conducted exercises around the Taiwan Strait and crossed the median line of the strait," Taipei's defence ministry said in a statement.

The median line is an unofficial but once largely adhered-to border that runs down the middle of the Taiwan Strait, which separates Taiwan and China.

Chinese incursions have become more common since Beijing declared in 2020 that the unofficial border no longer existed.

AFP journalists on the picturesque Chinese island of Pingtan saw a fighter jet flying overhead, prompting tourists to snap photos as it flew along the coast.

A Chinese military vessel was also visible sailing through the Taiwan Strait, they added.

China said it was ending cooperation with the United States on an array of key issues including climate change, anti-drug efforts and military talks, as relations between the two superpowers nosedive over Taiwan.

Beijing has insisted its war games are a "necessary" response to a visit to the self-ruled, democratic island by US House Speaker Nancy Pelosi, but Washington countered that China's leaders had "chosen to overreact".

The United States condemned China for cutting off bilateral cooperation in a number of key areas, and said Beijing can ease tensions over Taiwan by ending its "provocative" military drills.

National Security Council spokesman John Kirby said that China's decision to halt engagement on climate change and other issues was "fundamentally irresponsible."

He added that the US had nothing to rectify regarding US House Speaker Nancy Pelosi's trip to Taiwan, following demands from Beijing that Washington fix its "mistakes."

Mr Kirby told reporters at a briefing that the US would like to see tensions with China come down immediately.

"They think they're punishing us by shutting down this channel. They're actually punishing the whole world because the climate crisis doesn't recognise geographic boundaries and borders," he said.

He added that China can "go a long way to taking the tensions down simply by stopping these provocative military exercises and ending the rhetoric."

The only way out of the crisis in US-Chinese relations triggered by the visit to Taiwan by House Speaker Nancy Pelosi is for the United States to immediately rectify its mistakes, Jing Quan, a senior Chinese embassy official said.

Ms Pelosi defended her visit today, saying Washington would "not allow" China to isolate Taiwan.

"We have said from the start that our representation here is not about changing the status quo here in Asia, changing the status quo in Taiwan," she told reporters in Tokyo on the final leg of an Asia tour.

Taiwan's premier Su Tseng-chang, meanwhile, called for allies to push for de-escalation.

"(We) didn't expect that the evil neighbour next door would show off its power at our door and arbitrarily jeopardise the busiest waterways in the world with its military exercises," he said.

A Chinese military vessel sails off Pingtan island

Missiles over Taiwan

China's drills involved a "conventional missile firepower assault" in waters to the east of Taiwan, the Chinese military said.

The state-run Xinhua news agency said the Chinese military "flew more than 100 warplanes including fighters and bombers" during the exercises, as well as "over 10 destroyers and frigates".

State broadcaster CCTV reported that Chinese missiles had flown directly over Taiwan.

Japan also claimed that of the nine missiles it had detected, four were "believed to have flown over Taiwan's main island".

Taipei's military said it would not confirm missile flight paths, in a bid to protect its intelligence capabilities and not allow China "to intimidate us".

China's ruling Communist Party views Taiwan as part of its territory and has vowed to one day take it, by force if necessary.

But the scale and intensity of the drills have triggered outrage in the United States and other democracies.

"China has chosen to overreact and use the speaker's visit as a pretext to increase provocative military activity in and around the Taiwan Strait," a White House spokesman John Kirby said.

"The temperature's pretty high", but tensions "can come down very easily by just having the Chinese stop these very aggressive military drills", he added.

Japan lodged a formal diplomatic complaint against Beijing, with five of China's missiles believed to have landed in its exclusive economic zone.

Prime Minister Fumio Kishida called China's exercises a "serious problem that impacts our national security and the safety of our citizens" and called for an "immediate cancellation of the military drills".

But Chinese Foreign Minister Wang Yi said the "flagrant provocation" by the United States had set an "egregious precedent".

The manoeuvres are taking place along some of the busiest shipping routes on the planet, used to supply vital semiconductors and electronic equipment produced in east Asian factory hubs to global markets.

Taiwan's Maritime and Port Bureau has warned ships to avoid the areas being used for the Chinese drills.

"The shutting down of these transport routes - even temporarily - has consequences not only for Taiwan, but also trade flows tied to Japan and South Korea," Nick Marro, the Economist Intelligence Unit's lead analyst for global trade, wrote in a note.

Taiwan said the drills would disrupt 18 international routes passing through its flight information region while several international airlines said they would divert flights.

But markets in Taipei appeared to shrug off the tensions, with the Taiwan Taiex Shipping and Transportation Index, which tracks major shipping and airline stocks, up 2.3% early today.

And analysts broadly agree that despite all its aggressive posturing, Beijing does not want an active military conflict against the United States and its allies over Taiwan - just yet.

"The last thing Xi wants is an accidental war ignited," Titus Chen, an associate professor of political science at the National Sun Yat-Sen University in Taiwan, said.