Talks between the United Nations Command and North Korea have started regarding the case of US soldier Travis King, a UN official said on Monday.

"A conversation has commenced with the Korean People's Army through the mechanism of the armistice agreement," Lieutenant General Andrew Harrison of the US-led multinational command, responsible for overseeing the Korean War truce, said during a debriefing.

He added that their primary concern is the wellbeing of King, but refused to provide more details.

It is believed that King is being held in custody by North Korea.

Pyongyang has remained publicly silent about King, with the US saying that North Korea had been disregarding requests for information regarding Travis King's whereabouts.

The United States does not have any formal diplomatic ties with the North. The discussions with North Korea's military are taking place through an established mechanism under the Korean War armistice.

US soldier escapes to North Korea

US Army Private Travis King had completed his deployment in South Korea, as well as a prison sentence for assault, and should have returned to the US, but he escaped from the airport to join a private tour of the border.

He broke away from the group and crossed the demilitarized zone into North Korea, according to Pentagon spokeswoman Sabrina Singh.

The development comes around the time when tensions between Pyongyang and Washington have risen over the recent docking of a US nuclear-powered in South Korea.

North Korea's defense minister suggested last week that the docking of the submarine could be grounds for a nuclear attack by the North.

On Monday, a second US submarine reached port in South Korea.

ss/fb (AFP, Reuters, AP)