Taiwan accused the Chinese army of simulating an attack on its main island Saturday, as Beijing continued its retaliation for US House Speaker Nancy Pelosi's Taipei visit.

Relations between the two superpowers nosedived following Pelosi's trip to China's self-ruled neighbour -- which it claims as its territory -- prompting calls from the UN for an urgent de-escalation of tensions.

Beijing maintained some of its largest-ever military drills around Taiwan on Saturday -- exercises aimed at practising a blockade and ultimate invasion of the island, analysts say.

Taipei said it observed "multiple batches" of Chinese planes and ships operating in the Taiwan Strait, some of which crossed a demarcation line that divides the strait, but which Beijing does not recognise.

"They were judged to be conducting a simulation of an attack on Taiwan's main island," the island's defence ministry said.

In response, the democratic island's military mobilised air and land patrols and deployed land-based missile systems, the ministry said.

As of 5:00 pm local time (0900 GMT), Taiwan's army said "20 Communist planes and 14 ships were detected in the waters around Taiwan conducting joint air-sea exercises".

At least 14 of them crossed the median line, it said, forcing Taipei to scramble patrol planes to ward off the jets.

Taiwan's army released images on Saturday of a sailor on one of its frigates monitoring a Chinese ship within touching distance alongside the caption: "Absolutely not photoshopped!"

It also showed soldiers activating its land-based missile systems to track the Chinese planes.

US Secretary of State Antony Blinken, meeting with his Philippine counterpart on Saturday, said Washington was "determined to act responsibly" to avoid a major global crisis.

The environment became the latest victim of the geopolitical jousting a day earlier, as Beijing said it would withdraw from a series of talks and cooperation agreements with Washington -- most notably on climate change and defence cooperation.

China should not hold talks on issues of global concern such as climate change "hostage", Blinken said, as it "doesn't punish the United States, it punishes the world".

- New drills planned -

RTL

Chinese military exercises / © AFP

In a bid to show how close China's forces have been getting to Taiwan's shores, Beijing's military overnight released a video of an air force pilot filming the island's coastline and mountains from his cockpit.

And the Eastern Command of the Chinese army shared a photo it said was taken of a warship patrolling in seas near Taiwan, the island's shoreline clearly visible in the background.

The drills have also seen Beijing fire ballistic missiles over Taiwan's capital, according to Chinese state media.

Beijing said it would also hold a live-fire drill in a southern part of the Yellow Sea -- located between China and the Korean peninsula -- from Saturday until August 15.

Taiwan has remained defiant, insisting it will not be cowed by what Taipei's government earlier called its "evil neighbour".

Taiwan's foreign ministry told Beijing on Saturday to "immediately stop raising tensions and taking provocative actions to intimidate the Taiwanese people".

The Mainland Affairs Council, Taipei's highest policymaking body on China, also condemned the drills after Saturday's apparent simulation.

- Peace 'vital' -

The scale and intensity of China's drills have triggered outrage in the United States and other democracies.

Blinken and the foreign ministers of Japan and Australia issued a joint statement calling on China to halt the exercises after meeting on the sidelines of an Association of South East Asian Nations (ASEAN) summit in Cambodia.

But Beijing's decision to withdraw from hard-won cooperation on climate change has now sparked wider fears about the future of the planet.

RTL

The scale and intensity of China's drills have triggered outrage in the United States / © AFP

US National Security Council spokesman John Kirby told reporters in Washington the decision was "fundamentally irresponsible".

UN Secretary-General Antonio Guterres warned the two superpowers must continue to work together -- for the world's sake.

"For the secretary-general, there is no way to solve the most pressing problems of all the world without an effective dialogue and cooperation between the two countries," his spokesman Stephane Dujarric said.

- 'The new normal' -

With tensions over Taiwan having risen to their highest level in nearly 30 years, with an elevated risk of military conflict, experts told AFP the latest downturn in relations between the two countries could be long-lasting.

The suspension Friday of bilateral military and maritime dialogue while China continues its military exercises was "particularly worrisome", said Bonnie Glaser, a China expert at the German Marshall Fund.

"We don't know what else they will do," she said. "We just don't know if this is just a temporary thing."

John Culver, a former CIA Asia analyst, said in a discussion hosted by the Center for Strategic and International Studies that Beijing's main purpose with its military exercises was to establish a "new normal".

"The Chinese want to show... that a line has been crossed by the speaker's visit," Culver said.