The United States on Thursday said it would begin requiring travellers from Hong Kong, Macao and the mainland to take PCR tests for Covid-19 before departure, as Beijing questioned the scientific basis for measures limiting travel by its citizens.

Washington has joined countries such as India, Malaysia and Japan in imposing restrictions on Chinese travellers amid concerns about infections and easing pandemic curbs on the mainland.

American officials cited a lack of information on Covid variants from China for the decision, which will take effect on January 5. It applies to all travellers regardless of nationality or vaccine status and includes those going to the US via third countries.

Asked about travel restrictions at a news conference on Wednesday, Foreign Ministry spokesman Wang Wenbin said: "What is needed from all sides is a science-based response and coordinated approach to ensure the safety and security of cross-border travel and maintain the stability of the global supply and industrial chain, so as to promote a steady and sound recovery of the world economy.

"China believes that the pandemic measures should be science-based and appropriate and should not affect normal personnel exchanges."