South Korea's daily new coronavirus cases hit a fresh high of over 1,800 on Thursday with mass infections from a virus-hit Naval unit, while authorities are increasingly inclined to extend the toughest virus restrictions in the wider Seoul area amid no signs of letup.

The country added 1,842 COVID-19 cases, including 1,533 local infections, raising the total caseload to 184,103, according to the Korea Disease Control and Prevention Agency (KDCA).

The latest figure was the highest ever since the country confirmed the first case in January 2020, breaking the previous record of 1,784 on Wednesday.

Thursday's imported cases included 270 patients from the 301-member Cheonghae unit, which conducted an anti-piracy mission in waters off Africa, bringing the total number of such cases to a record high of 309.

It is the first time that the nation's imported cases surpassed 100.

The daily caseload has remained above the 1,000 threshold since July 7 due to the resurgence in the greater Seoul area, and the coronavirus has been spreading across the nation with increased activities in the summer season and the fast rise of the highly contagious delta variant.

The country added three more COVID-19 death, raising the death toll to 2,063.

The nation is in an uphill battle against the fourth wave of the pandemic with a rising proportion of patients in their 20s and 30s, as slightly over 30 percent of the 51.3 million population, mostly elderly people, health personnel and social service workers, have received at least one vaccine dose.

Concerns are also rising over the highly contagious delta variant, which has fast become the nation's dominant variant by taking up 76 percent of 1,255 locally transmitted variant cases over the past week.

Since last week, the Seoul metropolitan area has been under the highest level of the four-tier distancing measures, which ban gatherings of more than two people after 6 p.m. and place a 10 p.m. curfew on restaurants and cafes, as well as a ban on nightclubs and bars.

With no signs of cases abating, health authorities are considering extending the semi-lockdown measures in the wider Seoul area before the current restrictions expire Sunday.

In response to a sharp hike in new cases in non-capital areas, authorities tightened virus curbs to limit gatherings of more than four people across the nation, which went into effect Monday for two weeks.

As the summer holiday season nears, provincial governments began adopting stronger antivirus measures in major tourism spots to prevent virus transmission among incoming travelers.

A total of 16.4 million people, or 32.3 percent of the country's population, have received their first shots of COVID-19 vaccines, and 6.7 million people have been fully vaccinated, the KDCA said.

Of the newly confirmed domestic cases, 494 were from Seoul, 363 from the surrounding Gyeonggi Province and 130 from the western port city of Incheon.

The southeastern port city of Busan and the surrounding South Gyeongsang Province reported 102 and 90, respectively, as more people tested positive after going to bars and other entertainment venues.

The total number of people released from quarantine after making full recoveries was 163,073, up 1,439 from a day earlier.

The number of patients in critical condition came to 218, up four from the previous day. (Yonhap)