Prime Minister Kim Boo-kyum confirmed the government's intent to restore stricter social distancing measures during a virus meeting on Wednesday as the country set another one-day record in infections with 7850 cases, the fourth time this month the daily tally has exceeded 7000.

The country's death toll is now 4456 after 70 patients died in the most recent 24-hour reporting period, while a record 964 patients were in critical or serious condition.

Officials previously said the country's medical system could buckle if the number of serious cases topped 1000 because it would greatly hamper the ability of hospitals to respond not only to COVID-19 but also to other medical conditions.

"The government sees the current virus situation as serious and plans to enforce stronger social distancing measures," said Kim.

"We are considering measures that include further reducing the size of allowable social gatherings and imposing business-hour restrictions, and these steps will be confirmed and announced soon."

Some expect the new measures could be announced as early as Friday.

The virus surge has been a rude awakening for South Korea, which significantly eased social distancing rules and fully reopened schools in November in what officials had described as a first step towards restoring pre-pandemic normality.

In allowing larger social gatherings and lifting limits on indoor dining hours, officials had hoped improving vaccination rates would suppress hospitalisations and deaths even if the virus continued to spread.

However, there has been a surge in serious cases among people in their 60s or older, including those whose immunities have waned after being inoculated early in the vaccine rollout that began in February.

Officials had moderately sharpened social distancing rules last week, banning private gatherings of seven or more people in the capital Seoul and nearby metropolitan regions, and requiring adults to verify their vaccination status to use restaurants and other indoor venues.

Australian Associated Press