The Ethnic Unity and Progress Promotion Law aims to forge a "shared" national identity among ethnic groups, and states that people outside China who violate it could still be held liable.

Overseas rights groups and ethnic minority representatives have argued that the law could give the Chinese government more justification for targeting its opponents abroad.

Taiwan's foreign ministry expressed "its strong condemnation" on Wednesday, saying the legislation expanded "threats and intimidation against the people of our country and other nations".

"In the future, individuals from any country whose words or actions are not acceptable to China may become targets of the law or be pursued under it," the ministry said.

China claims Taiwan is part of its territory and has threatened to use force to annex the self-ruled, democratic island.

The law formalises longstanding policies to promote Mandarin as the language of education, official business and public spaces, and also contains provisions focusing on social cohesion and preventing terrorism and separatism.

A senior Chinese judicial official said last week that the clause allowing overseas enforcement was "legitimate, lawful (and) necessary".

But rights advocates say the law has been shaped to give Beijing more legal cover for pursuing long-existing policies to forcibly assimilate ethnic minorities with the Han majority.

UN rights chief Volker Turk has called for a repeal, and Tibetan and Uyghur advocates have urged countries to push China to cancel it, saying it aims to erase minority communities. Beijing consistently denies engaging in rights violations.

Taiwan's Mainland Affairs Council (MAC) said Taiwanese people already faced high risks travelling to China and warned Beijing now had "yet another law to fabricate charges".

"A closer examination reveals that the law is riddled with highly ambiguous legal concepts that leave room for subjective interpretation -- a consistent characteristic of the CCP's legal system," the MAC said in a statement, attributing the remarks to Deputy Minister Liang Wen-chieh.

The MAC said Beijing will use the law "as a legal basis to further suppress and persecute human rights in Xinjiang and Tibet, or to expand its threats against voices internationally that support or are friendly towards Taiwan".