China's aviation regulator ordered on Sunday a four-week suspension of a China Southern Airlines flight from Dhaka to Guangzhou in an effort to prevent imported COVID-19 cases.

Seventeen passengers on the June 11 flight from the Bangladeshi capital to the provincial capital of Guangdong tested positive for the novel coronavirus, meeting the conditions for a "circuit breaker" suspension of the flight route, the Civil Aviation Administration of China said in a statement.

In keeping with an international flights adjustment policy announced on June 4, the administration issued its first "circuit-breaker" directive and announced the four-week suspension would begin on June 22.

Earlier this month, China eased restrictions on international passenger flights contingent on epidemic risks being under control. Authorities highlighted the "reward and circuit breaker mechanism" for the carriers to increase or have flights suspended in accordance with the companies' epidemic control work.

Under the policy, airlines must suspend flights on a route for a week if five passengers test positive for coronavirus. If the number exceeds 10, the airline must suspend the flights for four weeks.

As an incentive, carriers may increase the number of international flights to two per week on a route if for three consecutive weeks no passengers test positive for the virus in nucleic acid tests.

Many airlines have been scaling up their epidemic prevention and control measures to comply with the administration's requirements.

Since Friday, Sichuan Airlines has required all travelers on its Cairo, Egypt, to Chengdu flight to take a nucleic acid test 72 hours before the flight and to check in with a valid written report of the test results. Passengers who cannot produce the document or who test positive for the virus are not permitted to board.

Lately, United Airlines has required passengers to complete a "health self-assessment" as part of its check-in process to confirm that they have not been diagnosed with COVID-19 in the past 21 days and that they haven't had symptoms such as fever, coughing, chills, muscle aches or sore throats in the past two weeks.

China registered 19 confirmed COVID-19 cases involving travelers from overseas on June 13, according to the National Health Commission. Seventeen of them arrived in Guangdong province.