South Korea on Tuesday ordered nightclubs, museums and buffet restaurants closed and banned large gatherings in and around the capital as a burst of new coronavirus cases sparked fears of a major second wave.

The country's "trace, test and treat" approach to curbing the virus has been held up as a global model, but it is now battling several clusters mostly linked to Protestant churches. Authorities reported 246 new infections on Tuesday, taking South Korea's total to 15,761, the fifth consecutive day of triple-digit increases after several weeks with numbers generally in the 30s and 40s.

Prime Minister Chung Sye-kyun said 12 high-risk business categories, including nightclubs, karaoke bars and buffet restaurants will cease operations from Wednesday in Seoul, Incheon and the neighbouring Gyeonggi province.

All public institutions in the areas, such as museums, will also close, he added, while indoor gatherings of more than 50 people, and outdoor ones of more than 100, will also be prohibited. Between them, the three areas account for half of South Korea's population. If the measures fail to contain the virus, it will bring a "great impact on our economy and people's livelihood", Chung said.

All church gatherings had already been banned in Seoul and Gyeonggi since Saturday, while sports events went behind closed doors again and residents were urged to avoid unnecessary travel. The largest current cluster is centred on the Sarang Jeil Church in Seoul, headed by a controversial conservative pastor who has tested positive himself.

A total of 457 cases are linked to that church as of Tuesday, but health authorities said the current situation was a "much bigger crisis" than South Korea's initial outbreak, when more than 5,000 people connected to a religious sect were infected.

That cluster was centred on the southern city of Daegu, but reports say that Sarang Jeil's members live all over the country. This time, "there is a risk of the virus spreading nationwide", said Kwon Jun-wook, deputy director general of the Central Disease Control Headquarters. "If the spread cannot be contained this week, daily life in the entire country may have to stop."