South Korea saw a continued decline in new coronavirus cases Sunday, but Seoul and its surrounding areas reported a continued rise in virus infections due to cluster transmission and imported cases.

The 81 new cases of COVID-19, detected Saturday, was slightly down from 94 new cases on Friday, brought the country's total cases to 10,237 and marked the 24th consecutive day that new infections have hovered around 100, according to the Korea Centers for Disease Control and Prevention (KCDC).

The country's death toll rose by six to 183, with more than half of fatalities being patients aged 80 or older, the KCDC said.

Two more deaths -- a 75-year-old woman and a 63-year-old man, both with underlying diseases -- were reported in the southeastern city of Daegu but have yet to be added to the official tally.

Of the 81 new COVID-19 cases, 40, or 49.4 percent, are imported cases involving entrants from foreign countries, the KCDC said.

Twenty-four of them were detected at quarantine checkpoints.

The country's total number of imported cases to came to 741, with 92 percent of them South Korean nationals.

The rate of imported cases out of total new confirmed COVID-19 cases has steadily increased from 34 percent on March 4 since health authorities began conducting such a tally.

The average fatality rate of local COVID-19 patients came to 1.79 percent while for those aged 80 or older came to a whopping 19.7 percent, the KCDC said.

Health authorities also said smokers are far more likely to develop serious COVID-19 cases compared with non-smokers.

"British health authorities recently cited a Chinese study that cited smokers or those with previous smoking history are 14 times more likely develop into serious cases compared to non-smokers," said KCDC Deputy Director Kwon Jun-wook.

A total of 36 additional cases were reported in Seoul and the surrounding areas that include Gyeonggi Province and the western port city of Incheon, bringing the total to 1,203 in the region, it said.

Seoul reported 24 new cases, bringing the total to 552, partly due to cases involving people from overseas, the KCDC said.

Gyeonggi Province reported 10 additional COVID-19 cases following a mass cluster case at Uijeongbu St. Mary's Hospital.

The number of daily new cases in the metropolitan area has continued to increase mainly due to mass cluster infection cases at major general hospitals and churches and imported cases.

Daegu and North Gyeongsang Province, the nation's two worst-affected regions, reported seven and four new cases, respectively, the KCDC said. The total number of cases reported in Daegu and the surrounding North Gyeongsang Province reached 6,768 and 1,314, respectively.

Despite a slowing but still continuing spread of cluster cases, the country on Saturday decided to extend its social distancing campaign for another two weeks until April 19.

The government-initiated campaign was first introduced on March 22. It prohibits mass gatherings while also advising people to voluntarily keep their distance from others.

Citizens are strongly urged to stay home, except for essential needs or jobs. The government has also strongly recommended that people suspend religious gatherings, indoor sports activities and visits to nightclubs and other entertainment venues.

"There can be catastrophic damage, like in other countries if we loosen up the current intensive social distancing that could lead to an increased number of patients," said Kwon.

The KCDC urged all industries in every part of the country to actively participate in the nationwide campaign to stop the recurrence of transmissions through unknown channels.

To stop coronavirus cases coming from abroad, all entrants from overseas -- both Koreans and foreigners -- are obliged to self-isolate at their residences or government-designated facilities for 14 days.

Starting Sunday, penalties against those who disturb quarantine efforts have been strengthened as health authorities strive to stop the recurrence of COVID-19 transmissions.

"There have recently been cases of giving false testimony or violating isolation measures," Kwon told reporters. "It is vital that people voluntarily take tests early for themselves, family members and society."

Under the measure, people who violate a mandatory 14-day self-quarantine measure or give false information during the quarantine process will face up to one year in prison or up to 10 million won ($8,090) in fines.

Previously, violators faced a fine up to 3 million won.

The measures come amid several cases in which entrants took a fever reducer at airport checkpoints before testing positive for COVID-19.

"Those who take fever reducers to avoid quarantine will be faced with stern punishment in accordance with relevant laws," Kwon said. "Taking a fever reducer has various side effects and dangers."

Foreigners who violate such measures can be immediately deported or not allowed to re-enter the country, the authorities said.

There have been several foreigners who were denied entry into the country for refusing to comply with the government's mandatory two-week self-isolation.

The KCDC said 138 more people have fully recovered and been released from quarantine, bringing the total number of cured people to 6,463.

As of Saturday, 3,591 were receiving treatment, down from 3,654 the previous day, according to the KCDC. (Yonhap)