China has been using every possible means to cause "chaos," a Taiwan source said ahead of a keynote speech on Thursday by President Lai Ching-te, as the island reported more Chinese warplanes in the run-up to its national day.

Lai, who took office in May after winning election in January, is detested by China, which calls him a "separatist". Beijing claims democratically governed Taiwan as its own territory, a view Lai and his government reject.

An official briefed on the wording of Lai's speech, describing the context around it, said Taiwan is in a "complex situation" and that China continues to harass the island militarily and psychologically.