Thousands of churchgoers in South Korea have been asked to quarantine after more than 300 worshippers tested positive for coronavirus.
The outbreak linked to the Sarang Jeil Church in Seoul is the nation’s largest in almost six months.
By the end of the weekend, 315 worshippers from the church had tested positive for COVID-19. Another 3,400 of its congregation have been asked to self-isolate.
South Korea had its fourth straight day of three-digit increases in new daily coronavirus cases on Monday, when 197 were reported.
On Sunday, 279 new cases were recorded, according to the Korea Centers for Disease Control and Prevention, amid fears the spike is getting out of control.
The government has urged people to stay at home and avoid travelling.
South Korea was hailed as a success story in the fight against the spread of coronavirus, thanks largely to an extensive testing and tracing system.
According to Johns Hopkins University, there have been more than 15,500 cases in South Korea and 305 deaths.
Health minister Park Neung-hoo urged people to stay home and for residents in Seoul and nearby Gyeonggi province to avoid visiting other parts of the country for two weeks.
The 279 new cases reported on Sunday were South Korea's biggest single-day jump since 367 on 8 March.
Infections were also reported in other major cities such as Busan and Daegu, which was the epicentre of the previous crisis in late February and March, when hundreds of new cases were reported each day.
During a virus meeting, president Moon Jae-in called for "pan-national" efforts to slow the spread of coronavirus.
He also instructed a review of plans for sharing hospital capacities between Seoul and nearby towns to ensure swift transport of patients so a spike of cases in one area does not overwhelm its hospital system.
There are concerns the spread could worsen after thousands of anti-government protesters rallied in Seoul on Saturday despite official pleas to stay at home.
It appears the protests, organised by conservative activist and church groups, mainly involved people over 60, who are considered at higher risk for complications linked to COVID-19.
The Sarang Jeil Church is headed by Jun Kwang-hun, a conservative pastor who has been highly critical of the president.
His church has been accused of failing to co-operate with health authorities.
Earlier this year, the Shincheonji Church of Jesus sect was linked to more than 5,000 cases in South Korea.
Its leader, Lee Man-hee, was arrested earlier this month on suspicion of hiding information about the group’s members from contact tracers.
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