South Korea's new virus cases fell back to below 40 on Saturday, but health authorities are keeping their guards up as imported cases and sporadic outbreaks in the country continue to put a strain on their efforts to contain the deadly virus.

The country added 39 cases, including 28 imported cases, raising the total caseload to 13,711, according to the Korea Centers for Disease Control and Prevention (KCDC).

The tally marked a sharp fall from 62 new virus cases reported on Monday, 61 cases on Thursday and 60 cases on Friday this week.

The daily rise in virus cases stayed below 40 on Tuesday and Wednesday, with 33 and 39 cases, respectively.

Infections coming in from overseas have been on a high plateau for weeks, with double-digit numbers for 23 consecutive days.

Imported cases have also been outnumbering local infections since Sunday.

Of the 28 additional imported cases, 12 were detected at quarantine checkpoints of airports and seaports.

By country, seven cases came from Uzbekistan, followed by five from the United States and three apiece from Pakistan and the Philippines. The total number of imported cases is now 2,032.

Kwon Jun-wook, deputy director of the Central Disease Control Headquarters, urged arrivals from foreign countries and their greeters, such as family members and friends, to strictly follow virus prevention measures.

So far, seven people have contracted the virus through secondary transmission from imported cases, he added, though such infections have not led to community spread in the country.

Of the cases coming in from overseas, South Korea has been keeping close tabs on workers returning home from Iraq after dozens of them tested positive for COVID-19 in recent days.

To bring the remaining workers home safely from Iraq, the government will send chartered flights to the Middle East nation next week.

Health authorities are also on alert over potential group infections tied to Russian-flagged vessels docked in the southern city of Busan. More than 20 crewmen were confirmed to have contracted the virus on three ships in recent days.

Among 154 ships that entered 11 South Korean harbors on Friday, health authorities said they have conducted onboard quarantine inspections on 75 vessels.

The number of new local infections dropped below 20 again. It had been under 20 from Monday to Thursday before the country reported 21 such cases on Friday.

Of the 11 local transmissions, nine were reported in the nation's Seoul metropolitan area -- six in Seoul, two in Gyeonggi Province and one in Incheon -- after more cases tied to door-to-door businesses and office building outbreaks were confirmed.

Health authorities said one student at Seongsu High School in Seoul tested positive for the novel coronavirus. However, 388 students and teachers who are suspected to have come in contact with the virus-infected student have tested negative for COVID-19.

The country's southern resort island of Jeju and the southeastern industrial city of Ulsan each added one case of the novel coronavirus.

South Korea reported one additional death from the virus, bringing the death toll to 294, according to the KCDC.

The total number of people released from quarantine after full recoveries stood at 12,519, up 59 from the previous day, while 898 are currently under treatment, down 21 from a day earlier.

The country has carried out 1,460,204 tests since Jan. 3. (Yonhap)