North Korea accused South Korea of sending ships across the disputed sea boundary to find the body of a man recently killed by North Korean troops, warning the alleged intrusion could escalate tensions.

South Korea said earlier that North Korea sent a message including a rare apology by leader Kim Jong Un over the shooting death last week of a South Korean government official found on a floating object in North Korean waters.

Officials in Seoul say the 47-year-old was likely attempting to defect to North Korea but little else is known about his motives.

“We urge the South side to immediately halt the intrusion across the military demarcation line in the West Sea that may lead to escalation of tensions,” the official Korean Central News Agency said.

“It arouses our due vigilance as it may lead to another awful incident.”

It confirmed North Korea notified South Korea about its account of the incident on Friday. But it did not say whether the notification included Mr Kim’s apology.

South Korea denied the North’s accusation. About 40 coast guard, navy and other ships and six aircraft continued searching waters south of the boundary on Sunday in case the man’s body drifts back, according to the coast guard. It said it has been searching for the past two days.

The poorly marked boundary is a source of animosities between the rival Koreas. They have fought at least three bloody naval skirmishes since 1999 and attacks blamed on North Korea killed 50 South Koreans there in 2010.

According to Friday’s North Korean message publicised by Seoul, North Korean troops shot the man because he refused to answer questions and attempted to flee.

It also said the troops burned his floating object in line with strict anti-coronavirus rules, after failing to find his body.

South Korea Koreas Missing Official
A South Korean marine boat patrols near Yeonpyeong island, South Korea (Baek Seung-ryul/Yonhap via AP)

South Korea said on Saturday it would request North Korea to launch an additional investigation.

Mr Kim’s apology was seen as an attempt to soothe anti-North sentiment in South Korea that could make it him difficult for him to win concessions in any negotiations.

Mr Kim is currently struggling to overcome worsening economic woes caused by US-led sanctions over his nuclear program and the pandemic that forced his country to close its border with China, its biggest trading partner.

While Mr Kim’s apology could help reduce the risk of escalation of tensions between the rivals, conservatives in South Korea have launched a political offensive on liberal President Moon Jae-in for failing to prevent the man’s death.