Flights scheduled for Friday are not covered by the new rule, since passengers would have done their tests before that day under previous requirements.
China also plans to impose dual-test requirements on travellers from Australia, Singapore and Japan from Nov. 8.
The European Union Chamber of Commerce in China said the antibody test was not widely available in many countries.
“(So) unfortunately, while technically leaving the door open, these changes imply a de facto ban on anyone trying to get back to their lives, work and families in China,” said the European Union Chamber of Commerce in China.
On Tuesday, China Southern Airlines 600029.SS, the country's biggest carrier by passenger load, said it would suspend transit services for passengers embarking from 21 countries, mostly African and Asian countries and including India and the Philippines.