Aiming to curb the spread of the coronavirus ahead of an all-important college entrance exam, South Korea will tighten anti-virus measures from today for two weeks. Measures include closing of clubs and bars, a ban on dine-in services at cafes, and a 20 per cent seating cap at religious events.

This comes as the country reported 271 new cases yesterday, the first time in six days that the daily figure has gone below 300.

The total tally has risen to 31,004, with 509 deaths so far.

Second Vice-Health Minister Kang Do-tae warned that the third wave of the pandemic is already under way, and it is harder to contain as the virus is spreading silently at small social gatherings where people tend to take off masks, and not due to big gatherings like in the two previous waves.

"Anti-virus measures and medical efforts would not be sustainable if we fail to break the chain of infections," he said yesterday, noting that over 2,000 cases were registered in the past week.

Yesterday's tally includes the highest daily figure in the military, with 33 new cases reported, out of whom 26 were traced to a cluster outbreak in an army unit in the border town of Cheorwon.

Thirty-seven of the unit's 200 members have been infected, with the rest waiting for test results.

Infections in the military have been growing since the middle of the month, reaching 263 to date. More than 3,500 military personnel are under quarantine.

On Sunday, the government announced it will raise the social distancing level to the third in a five-tier system in Seoul and greater Seoul (including Gyeonggi province and Incheon city) from today.

Under Level 2 social distancing, up from yesterday's Level 1.5, meetings and events with more than 100 people will be prohibited.

Five types of major entertainment facilities, including clubs and bars, will close, while karaoke rooms and indoor sports facilities can operate until 9pm. Restaurants will have to close dine-in services at 9pm, while cafes can run only on delivery and takeout.

Kindergartens and schools can have only one-third of their student population in school, while the rest have to learn online. Only high schools are allowed to run at two-thirds capacity.

Religious events can fill only 20 per cent of seats, and the figure is halved for sporting events.

Seoul city announced its own preemptive measures that will remain until the end of the year, such as reducing public transportation at night and banning rallies that involve 10 or more people.

Promotions to boost the local economy, such as a dining campaign by the Ministry of Agriculture and a travel coupon scheme under the Korea Tourism Organisation, will also be suspended.

Last week's spike in cases has sparked jitters among high school seniors and their parents.

Some 490,000 students are due to sit the College Scholastic Ability Test (CSAT) on Dec 3, an examination so important that working hours are delayed, flights postponed, and police cars dispatched to help ferry latecomers.

The exam was postponed by two weeks from last Thursday.

Education Minister Yoo Eun-hae has said CSAT is "not an easy test to postpone again", and the government will go all out to make sure it proceeds without any hindrance.

A two-week campaign was launched last Thursday to ensure cram schools, study cafes and other facilities frequented by high-schoolers will adhere to strict anti-virus measures, so as to keep exam takers safe from Covid-19.

"We can't let our guard down even the slightest bit," Ms Yoo said.