Taiwan dispatched forces on Wednesday in response to China's "live-fire" drills off the self-ruled island, Taipei's defense ministry said, condemning the exercises as dangerous.

China deployed 32 aircraft around Taiwan as part of a joint combat drill and announced "live-fire exercises" in an area about 40 nautical miles (74 kilometers) off the island's south, the ministry said in a statement.

Taiwan's military responded by sending sea, air and land forces to "monitor, alert and respond appropriately," the statement said.

China's People's Liberation Army "has blatantly violated international norms by unilaterally designating a drill zone 40 NM off the coast of Kaohsiung and Pingtung, claiming to conduct live-fire exercises without prior warning," the ministry said.

"This move not only caused a high degree of danger to the safety of international flights and vessels at sea, but is also a blatant provocation to regional security and stability."

China has ramped up the deployment of fighter jets and warships around Taiwan in recent years to press its claim of sovereignty over the island — which Taipei rejects.

The defence ministry said the live-fire exercises come after China held similar drills off Vietnam and Australia, and "prove that China is the only and biggest threat to peace and stability in the Taiwan Strait and the Indo-Pacific region."

The drills also come after Taiwan on Tuesday seized a Chinese-crewed cargo ship suspected of severing a subsea telecoms cable serving Taiwan's Penghu island group. 

There is growing concern in Taiwan over the security of its cables after a Chinese-owned cargo ship was suspected of cutting one northeast of the island this year.

China has threatened to use force to bring Taiwan under its control. And Taiwan fears China could sever its communication links as part of an attempt to seize the island or blockade it.

Taiwan is a potential flashpoint for a war between China and the United States, which is the island's most important backer and biggest arms supplier. 

While the United States is legally bound to provide arms to Taiwan, Washington has long maintained "strategic ambiguity" when it comes to whether it would deploy its military to defend the island from a Chinese attack.

Despite strong bipartisan support in the US Congress for Taiwan, there are fears that President Donald Trump might not consider the island worth defending if China attacked.

Taiwan President Lai Ching-te has already vowed to boost investment in the United States to reduce the trade imbalance and spend more on the island's military, while his government is also considering increasing US natural gas imports.