A South Korean crossed the heavily fortified border with North Korea in a rare defection, according to the South Korean military.

The Joint Chiefs of Staff said they carried out a search operation after detecting the person at around 9:20 p.m. Saturday on the eastern side of the demilitarized zone separating the two Koreas.

“We have confirmed that the person crossed the border of the military demarcation line at around 10:40 pm and defected north,” JCS said.

The JCS said it couldn’t confirm if the person was alive, but sent a notice to the North via a military hotline asking for protection.

The border crossing, which is illegal in South Korea, came as North Korea has implemented strict anti-coronavirus measures since the border was closed in early 2020, although it has not confirmed any infections.

Public and political outcry was sparked when North Korean troops shot dead a South Korean fisheries official who went missing at sea in September 2020, for which Pyongyang blamed anti-virus rules and apologized.

Two months earlier, North Korean leader Kim Jong Un declared a national emergency and cordoned off a border town after a North Korean defector who reportedly showed symptoms of COVID-19 illegally crossed the North-South border.

Prolonged blockages from the North and restrictions on interprovincial movement have also pushed the number of North Korean defectors arriving in the South to an all-time high.

Cross-border relations deteriorated after the denuclearization negotiations between Pyongyang and Washington were blocked in 2019.

South Korea and a United States-led UN force are technically still at war with North Korea since the 1950-1953 Korean War ended in an armistice rather than a treaty of peace.