Stricter COVID-19 prevention measures will come into force for people who travel to Shanghai from other cities, the local health authority said at a news conference on Monday.

According to Zhao Dandan, deputy director of the Shanghai Health Commission, the city will strengthen COVID-19 testing of people at key public transportation areas, including airports, railway stations and highways.

Landing and operations ashore are prohibited for ships from domestic medium and high-risk areas.

In addition, employees in the tourism industry are required to take a nucleic acid test once a day and tourists must hold negative nucleic acid reports from within 48 hours prior to their arrival, Zhao said.

Shanghai reported three asymptomatic COVID-19 cases outside the quarantined and controlled population on Monday.

Three places in Pudong New Area, Putuo district and Songjiang district, where the cases live, were categorized as high-risk areas.