Beijing will "never tolerate" Taiwan's separation from China, a spokesman at the mainland's top Taiwan body said Wednesday, after President Tsai Ing-wen was inaugurated for a second term.

China considers the democratic, self-governing island as part of its territory, and has repeatedly advocated for its eventual reunification with the mainland - using military force if necessary.  

Ma Xiaoguang, spokesman for the Taiwan Affairs Office, said China had "sufficient ability to defend national sovereignty and territorial integrity", according to official state news agency Xinhua.

Beijing would "never tolerate any separatist activities or external forces interfering in China's internal politics", he said.

Ma said China said was willing to "create a vast space for peaceful reunification", but will "not leave any room for all forms of Taiwanese independence separatist activities".

China would adhere to the principles of "peaceful reunification" and "One Country, Two Systems", he added, referring to the political framework used to govern the semi-autonomous city of Hong Kong. 

Tsai is loathed by Beijing because she views Taiwan as a de facto sovereign state and not part of "one China".

In recent years cross-strait ties have come under more pressure as China has isolated Taiwan from its few remaining diplomatic allies and flexed its military might in the strait separating the two.