People crowd a market in Busan, South Korea on Friday as the Mid-Autumn Festival approaches. South Korea reported 126 more cases of the COVID-19 as of midnight Thursday local time compared to 24 hours earlier, raising the total number of infections to 22,783. Photo: VCG

South Korea raised its coronavirus alert to the second-highest level in Seoul and surrounding areas Sunday as authorities struggle to contain a fresh outbreak.

The country largely brought the virus under control with a "trace, test and treat" approach, but in recent weeks new infections have jumped from around 100 a day to more than 500.

South Korea confirmed 631 new cases on Sunday - the highest in nine months - with the majority in the greater Seoul region, according to the Korea Disease Control and Prevention Agency.

By global standards the figure remains low, but the rise has alarmed authorities, who have tightened social distancing measures.

"We are facing the biggest crisis in our fight against COVID-19," Prime Minister Chung Sye-kyun said Sunday.

All gatherings of more than 50 people will be banned and professional sports will be held behind closed doors with no spectators.

Cafes will continue to serve only takeaways, while restaurants must close by 9 pm, with only deliveries permitted afterward.

The tightened measures will be in place until the end of 2020, Chung said in a statement.

South Korea endured one of the worst early novel coronavirus outbreaks outside Chinese mainland, but never imposed the kind of lockdowns ordered in much of Europe and other parts of the world.

AFP