BEIJING, Oct. 14 (Xinhua) -- Issues between the two sides of the Taiwan Strait are domestic affairs between compatriots within the same family, which allow no external interference, said a Chinese mainland spokesperson on Wednesday.

Zhu Fenglian, a spokesperson for the Taiwan Affairs Office of the State Council, made the remarks in response to a query about a United States-related proposal by the Chinese Kuomintang (KMT) party in Taiwan.

Reiterating that Taiwan is an inalienable part of China, Zhu noted that it is an unchangeable historical and legal fact that both sides of the Taiwan Strait belong to one China.

"We firmly oppose any separatist act to create the so-called 'Taiwan independence,' 'two Chinas' or 'one China, one Taiwan,'" Zhu said, stressing that such bottom-line principles should never be tested.

Zhu said the fundamental cause for the complicated situations and tensions across the Taiwan Strait at present is that the Democratic Progressive Party authority in Taiwan, colluding with external forces, has continuously taken provocative actions seeking "Taiwan independence."

People with a sense of justice and responsible political parties on the island should be aware of, remain vigilant to, and firmly oppose the moves, Zhu said, adding that any statement or action violating the one-China principle or undermining the fundamental interests of the Chinese nation will be resolutely opposed by all Chinese people.

She said the mainland is closely following the move by some KMT members in seeking a change to the party's name, which had been questioned by the media and all walks of life on the island.