North Korean leader Kim Jong-Un has issued a detailed threat to "wipe out" a small South Korean island in a further escalation of already elevated military tensions on the Korean peninsula.

In a visit Monday to border artillery units, Kim identified Baengnyeong Island on the South side of the disputed maritime frontier as a priority target in the event of conflict.

The visit coincided with the launch of a joint South Korea-US military drill that has prompted Pyongyang to announce the scrapping of the 60-year-old Korean War armistice, along with non-aggression pacts signed with the South.

The North has also threatened nuclear strikes on the United States and South Korea as a reprisal for UN sanctions imposed over its third nuclear test last month.

While most of these statements have been dismissed as rhetorical bluster, the threat to Baengnyeong, which has 5,000 civilian residents as well military units, is highly credible and carries the weight of precedent.

In 2010, the South Korean naval vessel Cheonan was sunk in the area of Baengnyeong with the loss of 46 lives, and later the same year North Korea shelled the nearby island of Yeonpyeong, killing four people.

Kim Jong-Un's warning, reported Tuesday by the state-run Korean Central News Agency, was notable for its detail and hostility, as he briefed artillery officers on turning the island into "a sea of flames".

"He told the commander to photograph enemy positions engulfed in flames during a battle and send pictures to the Supreme Command," KCNA said

"Once an order is issued, you should break the waists of the crazy enemies, totally cut their windpipes and thus clearly show them what a real war is like," Kim said.

Priority targets on the island included radar posts, Harpoon anti-ship missile launchers, 130mm multiple rocket stations and 150mm self-propelled howitzer batteries, Kim said.

An administrative official on Baengnyeong, Kim Young-Gu, said civilian emergency shelters on the island had been fully stocked and all village councils put on high alert.

"It's not like there's a mass exodus of panicked islanders to the mainland. But to be honest with you, we're a bit scared," Kim told AFP by telephone.

Television reports said residents of several border islands had taken to sleeping in their clothes in preparation for a night-time alert.

Kim Jong-Un also clarified engagement rules against naval vessels that encroach on the maritime border recognised by Pyongyang, which does not recognise the frontier drawn up by the UN after the 1950-53 Korean War.

Artillery units should fire warning shells on enemy warships sailing close to the border and then destroy them if they cross, Kim was quoted as saying.

The disputed sea border off the west coast was the scene of deadly naval clashes in 1999, 2002 and 2009.

Source: AFP