Sharjah24 – AFP: China is due on Thursday to kick off its largest-ever military exercises encircling Taiwan, in a show of force straddling vital international shipping lanes following a visit to the self-ruled island by US House Speaker Nancy Pelosi.

Pelosi left Taiwan Wednesday after a less than 24-hour visit that defied a series of increasingly stark threats from Beijing, which views the island as its territory.

The House speaker, second in line to the presidency, was the highest-profile elected US official to visit Taiwan in 25 years.

She declared her presence made it "unequivocally clear" that the United States would "not abandon" a democratic ally like Taiwan.

Her trip sparked a furious reaction from Beijing, which vowed "punishment" for those that had offended it and announced military drills in the seas around Taiwan -- some of the world's busiest waterways.

The exercises, set to begin at 12:00 pm (0400 GMT), will involve "training activities including live-fire drills", according to an announcement in state media.

They will take place in multiple zones encircling Taiwan -- at some points within just 20 kilometres (12 miles) of the island's shore -- and will conclude at midday on Sunday.

Taipei has condemned the plans, warning they threaten the security of the East Asia region.

"Some of the areas of China's drills breach into... (Taiwan's) territorial waters," defence ministry spokesman Sun Li-fang said at a press conference Wednesday.

"This is an irrational move to challenge the international order."