Seven American service members have tested positive for the new coronavirus upon arrival in South Korea from the United States this month, the US Forces Korea (USFK) said Thursday.

Four of them arrived at Osan Air Base in Pyeongtaek, some 70 kilometers south of Seoul, on US government chartered flights, and the other three arrived on international commercial flights at Incheon International Airport, west of Seoul, earlier this month, according to the US military.

Of them, four individuals tested positive on their first mandatory COVID-19 test prior to entering quarantine, and the others were confirmed to have been infected with the virus on a subsequent test while in quarantine.

They all have since been transferred to an isolation facility designated for coronavirus patients at Camp Humphreys in Pyeongtaek, USFK added.

All USFK-affiliated individuals arriving in South Korea are required to undergo a virus test and are quarantined for 14 days.

Medical personnel administer a second test prior to their release.

The latest cases brought the total number of USFK-related infections to 238, most of whom tested positive upon their arrivals here.

"A thorough cleaning of all transportation assets and quarantine rooms has been completed," USFK said in a statement.

"None of the new arrivals have interacted with anyone residing within USFK installations or the local community."

Starting Aug. 30, the US Department of Army has required all American soldiers, family members and other related civilians to have a negative test result for the new coronavirus prior to their departure for South Korea.

But the requirement does not apply to service members from the Navy, the Air Force and the Marine Corps.

On Thursday, South Korea added 121 more COVID-19 cases, including 104 domestic infections, raising the total caseload to 25,543, according to the Korea Disease Control and Prevention Agency (KDCA). (Yonhap)