Shanghai reported 18 new COVID-19 cases that originated abroad and zero locally-transmitted infections on Sunday, local health authorities said on Monday morning.

All the imported cases were Chinese nationals flying from the United Arab Emirates (UAE).

Among them, three passengers arrived in the city on August 6, having flown directly from the UAE a day earlier. The remaining 12 landed in the city on August 7 coming from the Gulf country via in Sri Lanka.

The Civil Aviation Administration of China issued a four-week suspension for the flight as part of a mechanism to limit the number of imported infections.

The aviation authorities did not say whether the two flights were operated by the same carrier and which airline or airlines will be implicated in the decision.

Since June, China has eased its travel restrictions, in place since the coronavirus outbreak, provided the risk of imported coronavirus cases is managed. It set up a mechanism whereby carriers would be rewarded or punished depending on how many of their passengers, if at all, test positive for COVID-19.

Airlines are asked to suspend flights on a China-bound route for a week if at least five passengers test positive for the virus. If the number exceeds 10, flights would be suspended for four weeks.

If all nucleic acid test results were negative for three consecutive weeks on the same route, the carrier may fly two weekly passenger flights.

Once the "circuit-breaker" period ends, the airline can resume its normal weekly passenger flights.

Shanghai authorities have implemented strict epidemic prevention measures such as health declaration, temperature checks and quarantine arrangement for inbound flights.

Passengers with fever and other coronavirus symptoms are transferred to designated medical institutions for diagnosis and treatment. Nucleic acid testing is carried out for all arrivals.