China firmly opposes any visit by "Taiwan independence" separatist forces to countries that have diplomatic relations with China under any pretext, Foreign Ministry spokeswoman Mao Ning said on Tuesday.

Mao made the remarks when asked about former Taiwan "leader" Tsai Ing-wen's upcoming visit to the Czech Republic this month.

Tsai, who stepped down in May, will visit Prague and deliver a speech at a Forum 2000 conference, which begins on Oct 13, three sources briefed on the matter told Reuters.

The spokeswoman urged Czech and other relevant countries to adhere to the one-China principle, respect China's sovereignty and territory integrity, refrain from providing convenience to "Taiwan independence" separatist forces and damaging bilateral ties.

Mao also warned the Democratic Progressive Party authority that seeking independence is a dead end.

"Any political manipulation or attempts to seek independence by soliciting external support will be futile," she said.