North Korean leader Kim Jong Un apologised on Friday for the shooting death of a South Korean man to prevent the spread of the novel coronavirus, the South’s national security adviser said, as public and political outrage over the killing grew.

The apology came in a letter from the North’s united front department, which handles cross-border ties, to South Korean President Moon Jae-in a day after South Korean officials said the North’s soldiers killed the man, doused his body in fuel and set it on fire.

The rare conciliatory message from the North Korean leader came as Moon faced intense political fallout over the incident, which coincided with a renewed push by him for engagement with North Korea.

“Chairman Kim Jong Un asked to convey his feeling that he is greatly sorry that an unexpected unsavoury incident occurred in our waters which hugely disappointed President Moon Jae-in and compatriots in the South,” the adviser, Suh Hoon, told reporters.

Suh said the letter was a response to requests for an explanation for the incident and included a promise to prevent any recurrence.

North Korea expressed hope the incident would not undermine recent efforts to foster trust, Suh said, adding Moon and Kim had exchanged letters this month.