People wearing face masks watch a television news broadcast showing a speech of South Korean President Moon Jae-in on the occasion of the third anniversary of his inauguration, at a railway station in Seoul on Sunday. Photo: AFP

South Korea's capital has ordered the closure of all clubs and bars after a burst of new cases sparked fears of a second coronavirus wave as President Moon Jae-in urged the public to remain vigilant.

The nation has been held up as a global model in how to curb the virus, but the order from the Seoul mayor on Saturday followed the new infection cluster in Itaewon, one of the city's busiest nightlife districts.

More than two dozen cases were linked to a 29-year-old man who tested positive after spending time at five clubs and bars in Itaewon last weekend.

Health authorities have warned of a further spike in infections, with around 7,200 people estimated to have visited the five establishments identified.

"Carelessness can lead to an explosion in infections," Seoul mayor Park Won-soon said, adding the order will remain in effect indefinitely.

Park asked those who visited those clubs and bars to come forward voluntarily.

Of the 18 new South Korean cases reported on Saturday, 17 were tied to the Itaewon cluster, according to the Korea Centers for Disease Control and Prevention.

The jump in new infections comes as everyday life in South Korea has slowly started returning to normal, with the government relaxing social distancing rules Wednesday.

President Moon said Sunday that the fresh infection cluster had "raised awareness that even during the stabilization phase, similar situations can arise again anytime."

"It's not over until it's over," Moon said during a speech marking his third anniversary of taking office.

"While keeping enhanced alertness till the end, we must never lower our guard regarding epidemic prevention," he added.

Moon has enjoyed growing public support on the back of his government's handling of the virus, which led to a landslide victory for his ruling party at the parliamentary elections in April.

The country reported 34 new cases on Sunday - its largest daily increase in a month - taking the total to 10,874.

South Koreans reacted with fury and fear to the news of the latest spike in infections.

"What a disaster... Is this the beginning of another wave of a nationwide coronavirus outbreak?" wrote one internet user.

Another commentator added: "It's outrageous how selfish and ignorant people can be. We should all stay home."

The country endured one of the worst early outbreaks of the disease outside the Chinese mainland, and while it never imposed a compulsory lockdown, strict social distancing had been widely observed since March.

But it appears to have brought its outbreak under control thanks to an extensive "trace, test and treat" program that has drawn widespread praise.

AFP