The parents of a runaway South Korean soldier who has fled to a forest after allegedly killing five comrades near the North Korean border has pleaded with him to surrender.

South Korean troops have exchanged fire with a runaway soldier who was surrounded in a forest after he killed five comrades near his North Korea border outpost, and brought in his parents to persuade him to surrender, a defence official said.

North Korea denied today that it ever admitted that it had a secret nuclear weapons programme and said it would unleash a “sea of fire” if the United States persists in challenging the communist country.