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

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.

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.

With no signs of cases abating, health authorities are widely expected to extend the semi-lockdown measures in the greater Seoul area for another two weeks.