President Moon Jae-in on Sunday warned of stern responses to unlawful acts by some church members that have hampered the country's anti-virus efforts, after a far-right pastor and his followers staged massive rallies in violation of a state ban amid a surge in new coronavirus cases.

On Saturday, more than 10,000 people took part in rallies in downtown Seoul, including one led by a far-right group, and participated in by pastor Jun Kwang-hoon and other members of Sarang Jeil Church in Seoul.

He eventually failed to host an anti-government rally as planned after the city government banned large gatherings out of COVID-19 concerns. He, however, participated in another rally leading his followers from across the country while failing to take appropriate quarantine measures, according to officials. More than 100 coronavirus patients were believed to have been connected to the church at that time.

"It is a very senseless act that hampers efforts of the whole people to contain the spread of the new coronavirus. It is a clear challenge to the national disease control and prevention system, and an unforgivable act that threatens the lives of the people," Moon said in his Facebook message.

The government will take "very stern and strong measures even by resorting to compulsory means," Moon added.

"We are at a critical juncture, as a large number of new cases are expected to be reported for some time being," Moon said, expressing sorry for causing concern over the spread of the coronavirus at a time when the people have faced difficulties after recent heavy rains.

"Please follow the government's quarantine measures thoroughly. The government will trust the people and do its best to overcome the current difficulties," Moon added.

On Sunday, South Korea reported 279 additional COVID-19 cases, a surge from 166 new cases the previous day, according to the Korea Centers for Disease Control and Prevention. It is the first time that the country reported more than 200 new daily infections in five months.

Cases linked to Sarang Jeil Church have totaled 193 nationwide, according to the Seoul metropolitan government.

The central government said it will file a complaint against Jun with related authorities for his alleged violation of self-quarantine obligations and the disruption of the country's quarantine work by submitting a false list of suspected coronavirus patients among his followers.

Separately, the Seoul municipal government also vowed to report him and other church officials to law enforcement authorities for their suspected violation of the country's infectious disease prevention act.

"Pastor Jun broke the self-isolation rule and spread false information to deliberately delay virus tests for church members," acting Mayor Seo Jeong-hyup said in a press briefing Sunday.

During a recent media report, Jun claimed that the COVID-19 infections among his church members seem to have been caused by "virus terrors by outside forces."

A total of 4,066 members are required to undergo virus tests, but the authorities have failed to reach 669 people, according to the city government. (Yonhap)