SEOUL — South Korea on Tuesday announced the closure of nightlife venues and in-person services at churches in the greater Seoul area after a coronavirus cluster of more than 400 cases emerged at a megachurch led by a vocal critic of President Moon Jae-in.

The Sarang Jeil Church has been identified as a hotbed of the novel coronavirus in the South Korean capital, which managed to keep its virus numbers at single or double digits in recent months.

It also exposed the challenges South Korea’s many independent churches and religious sects pose for the country’s health authorities, who have been hailed around the world for successes in controlling covid-19, the disease caused by the coronavirus, and tracking cases.

In February, a fringe religious group, Shincheonji Church of Jesus, became the center of South Korea’s outbreak, with more than 5,000 cases linked to the church. Earlier this month, the church’s leader was arrested on charges of obstructing the government’s infection-control measures by withholding necessary information.

In the current case, the Sarang Jeil Church’s pastor, the Rev. Jun Kwang-hoon, tested positive for the virus on Monday. He had defied health rules to hold services and anti-Moon protests, including one on Saturday attended by thousands of demonstrators.

Jun has been rallying right-leaning Christians under the slogan that Moon is “communizing” South Korea with policies such as outreach to North Korea. Jun’s speeches are often filled with controversial and sometimes outlandish claims against Moon’s government.

The closure orders on churches will take effect on Wednesday with a host of social distancing restrictions following triple-digit increases in the nation’s virus caseload for five consecutive days.

South Korea, a country of 51 million, reported 246 new cases of the virus on Tuesday, bringing up the country’s confirmed cases to 15,761. With 306 coronavirus deaths, the country’s fatality rate from the virus is below 2 percent.

South Korean Prime Minister Chung Sye-kyun warned of a “large-scale nationwide transmission” if the church cluster cannot be contained.

In a nationally televised briefing, Chung announced a ban on large gatherings and closure of churches and nightlife venues such as karaoke bars and clubs.

“We are experiencing difficulties searching for members and visitors to Sarang Jeil Church where the infection cluster is currently the biggest,” Chung said. He added that an inaccurate member list provided by the church makes it hard to track members for tests or quarantine.

A day after Saturday’s rally, Moon himself condemned the rallygoers and church members who ignored health officials’ pleas to stay at home and “spread the virus to protesters from all over the country.”

“This is a clear confrontation against the country’s disease-prevention system and an unpardonable act against the safety of our people,” Moon said in a statement. “Our government cannot but use force to take strict and strong actions.”

The church’s leader, Jun, said in an interview with a Christian media outlet that his church is a victim of a “virus terror” by an outside force. Health officials said they were experiencing difficulties testing church members because of rumors that authorities rig test results to come out positive.

South Korea’s government filed a complaint against Jun this week for defying quarantine orders, underreporting the church’s membership to hinder contact tracing efforts and discouraging congregants from getting coronavirus tests.

Jun was arrested earlier this year for violating election laws by endorsing specific political parties at his rallies before the beginning of the official election period. He had since been released on bail and continued holding services and anti-government rallies.

Denyer reported from Tokyo.