SEOUL, South Korea — South Korea has reported 20 new coronavirus cases, including nine in the Seoul metropolitan area, as authorities scramble to stem transmissions while proceeding with a phased reopening of schools.

The figures announced Friday by the Korea Centers for Disease Control and Prevention brought national totals to 11,142 cases and 264 deaths. Nine other new cases were linked to international arrivals.

South Korea was reporting around 500 new cases a day in early March but has since managed to stabilize infections with aggressive tracing and testing. Officials have eased social distancing measures and began reopening schools, starting with high school seniors on Wednesday.

But students at dozens of schools in Incheon, near Seoul, were sent back home after some tested positive after visiting a karaoke room or taking private classes from a virus carrier.

Health Minister Park Neung-hoo pleaded with people Friday to avoid visiting karaoke rooms or computer gaming centers near schools to lower infection risks for students.

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BEIJING — China has reported four new confirmed cases of the coronavirus.

Another 372 people are in isolation and undergoing monitoring for being suspected cases or after testing positive without showing symptoms, and 82 remain in the hospital for treatment of COVID-19.

The new cases come as China opens the annual session of its ceremonial parliament, the National People’s Congress, which is being held largely behind closed doors in Beijing to avoid cross-infections as the country looks to avoid a second wave of cases.

China has reported 4,634 deaths among 82,971 cases since the virus was first detected late last year in Wuhan. The central Chinese industrial city moved this week to completely ban the raising and sale for human consumption of wild animals that are considered a key vector for transmission of the virus from bats to people.