North Korea expressed regret on Friday that it shot dead a missing South Korean to prevent the spread of the coronavirus, the South's national security adviser said, amid growing political and public backlash.

North Korea's United Front Department, in charge of cross-border ties, sent a letter to South Korean President Moon Jae-in's office a day after Seoul officials said North Korean soldiers killed a South Korean before dousing his body in oil and setting it on fire.

The rare message came as Moon faced intense political fallout over the incident, which coincided with a renewed push for policy to engage Pyongyang.