SEOUL, Feb. 17 (Reuters) - South Korea’s Prime Minister Chung Sye-kyun on Wednesday warned against loosening enforcement of social distancing rules after the number of new coronavirus cases hit the highest levels in nearly 40 days.

The government relaxed distancing curbs starting this week, after getting on top of a third wave of COVID-19 outbreaks that peaked at about 1,200 daily cases in late December.

But the numbers shot back up in just three days, topping 600 for the first time in 39 days on Tuesday, after a ban on nighttime entertainment facilities was lifted and a restaurant curfew extended by one hour to 10 p.m.

Chung said there were signs of lax discipline, singling out nightclubs opening at 5 a.m. and people partying at a hotel after the curfew.

“We’ve eased distancing to help small business owners maintain their livelihoods, not to keep a slack rein on the virus,” he told a televised meeting. “The third wave is not over ... now is never the time to loosen up.”

The Korea Disease Control and Prevention Agency (KDCA) reported 621 cases as of Tuesday midnight, from in the 300-400s in the previous few days as testing increased after last week’s Lunar New Year holidays.

Authorities are on high alert as more cluster infections could emerge because of the holidays, during which millions of Koreans travelled across the country to visit relatives or tourist sites.

If the numbers continue to surge, the government will consider reinstating stricter curbs to prevent a fourth wave before its vaccination campaign begins on Feb. 26, said Son Young-rae, a senior health ministry official.

“March and April are when another wave is most likely to occur because vaccination could bring weaker vigilance in general and public fatigue toward distancing is rising,” Son told reporters.

South Korea’s total infections grew to 84,946 cases, with 1,538 deaths.