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Passengers flying from the U.S. to China must provide proof of negative COVID-19 tests taken within 72 hours of the flight, Chinese officials have announced.

And any travelers passing through or changing airports in countries that Chinese officials list as requiring the screening must have proof of negative coronavirus tests within three days of boarding the last layover destination, Bloomberg reported. 

The new rules take effect Sept. 15.

The new regulations are part of escalating restrictions imposed on U.S. citizens by Beijing, amid tense counter measures taken by Washington.