"Supporters of Taiwanese separatism must stop in time to avoid disaster, repent and return to the right path. Otherwise they will become the scum of the Chinese nation and be condemned by history," said He Lei, former vice president of the Academy of Military Sciences.

"If we are forced to use force to settle the Taiwanese issue, they will be held responsible. In other words, they will inevitably be considered war criminals," the lieutenant general said, adopting a martial tone in a meeting with journalists.

China still sees Taiwan as part of its territory to be reunified, despite the two sides being ruled separately since they split in 1949 after a civil war won by Mao Zedong's communists.

General He's warning to Taiwanese separatists comes after President Xi Jinping last week said China would not renounce the option of using force to recover the island and vowed that reunification was "inevitable".

Taiwan considers itself a sovereign state, with its own currency, political and judicial systems, but has never declared formal independence from the mainland.

Relations have been strained since the 2016 election of President Tsai Ing-wen, who has refused to acknowledge Beijing's stance that the island is part of "one China".