South Korea's daily new coronavirus fell back to the 1,600s on Sunday due to fewer tests over the weekend, health authorities said, yet tough restrictions are to be extended to battle the fast surge of the outbreak driven by the more transmissible delta variant.

The country added 1,628 more COVID-19 cases, including 1,590 local infections, raising the total caseload to 236,366, according to the Korea Disease Control and Prevention Agency (KDCA).

Sunday's tally was down from 2,052 on Friday and 1,880 on Saturday, the KDCA said.

It also marks the first time since July 29 that the daily new cases have fallen back to 1,600s.

But the decline was attributable to less testing over the weekend. Daily cases surpassed 1,000 on July 7 and have stayed above the mark for 47 days in a row.

The country added 13 more deaths from COVID-19, raising the death toll to 2,215, the KDCA said.

The fourth wave of the pandemic has shown no signs of letup although stringent virus restrictions have been in place amid slower-than-expected vaccinations.

The wider Seoul area, where half of the nation's 52 million population lives, has been under Level 4 restrictions, the highest in the four-tier virus curbs, for the past six weeks, while most other areas have implemented Level 3 distancing for the last four weeks.

The current social distancing measures will be extended starting Monday until Sept. 5.

Under the tougher measures, restaurants and cafes will be required to close at 9 p.m., an hour earlier than the current nighttime curfew.

The semi-lockdown measures prohibit gatherings of more than two people after 6 p.m., and ban the operation of nightclubs and other entertainment venues. 

As of Sunday, 25.9 million people, or 50.4 percent of the population, have received their first shots of COVID-19 vaccines, and 11.4 million people have been fully vaccinated, the KDCA said.

Currently, those aged between 18 and 49 are making advanced reservations for vaccine shots, with the rate standing at 61.3 percent of the eligible age group, the agency said.

The government aims to vaccinate at least 70 percent of the nation's population by September to create herd immunity in November, but the delayed supply of vaccines by US drugmaker Moderna Inc. has sparked concerns over the feasibility of its plan.

In response to media reports that Romania plans to donate 450,000 doses of Moderna's vaccines nearing their expiry date to South Korea, the foreign ministry said talks have been under way with the Romanian government for vaccine cooperation.

Of the newly confirmed domestic cases, 493 were from Seoul, 513 from the surrounding Gyeonggi Province and 64 from the western port city of Incheon, the authorities said. The total tally from the wider Seoul area came to 1,070.

The new daily cases from the area have been a four-digit number for four days in a row.

The southeastern port city of Busan identified 111 new patients, and the North Gyeongsang Province had 56 more, they said.

There were 38 imported cases, down from 66 reported a day earlier, the KDCA said.The number of patients with serious symptoms across the country reached 395, it said.

The total number of people released from quarantine after making full recoveries was 206,276, up 1,758 from the previous day. (Yonhap)