North Korea has sentenced one of three detained Americans to six years of hard labour, a statement carried by state media said.

In the statement issued following a trial on Sunday, Pyongyang said Matthew Miller committed "hostile acts" as a tourist in the isolated country.

Miller, 26, of Bakersfield, California, is said to have torn up his visa at Pyongyang's airport and demanded asylum.

They use human beings, and in this case Americans citizens, as pawns. And we find that both objectionable and distressing.

- Daniel Russel, US assistant secretary of state

In an earlier interview with AP, Miller and the other men called for Washington to send a high-ranking US representative to make a direct appeal for their freedom.

The US has repeatedly offered to send its envoy for North Korean human rights issues, Robert King, to Pyongyang to seek a pardon for Miller and other US detainees, but without success. His planned visits were cancelled twice.

On Friday, Assistant Secretary of State Daniel Russel, the senior US diplomat for East Asia, accused North Korea of using US citizens as human "pawns".

"This is the way that they play," he told Reuters news agency. "They use human beings, and in this case American citizens, as pawns. And we find that both objectionable and distressing."

North Korea, which is under heavy UN sanctions related to its nuclear and missile programme, is widely believed to be using the detained US citizens to extract a high-profile visit from Washington, with whom it has no formal diplomatic relations.

Other Americans held

In the past, former US Presidents Bill Clinton and Jimmy Carter had visited North Korea to secure the release of detained Americans.

North Korea has yet to announce a trial date for fellow US citizen Jeffrey Fowle, 56, from Miamisburg, Ohio, who was arrested in May this year for leaving a bible under the toilet of a sailor's club in the eastern port city of Chongjin.

A third American, Korean-American missionary Kenneth Bae, is serving out a 15-year sentence for alleged "hostile acts".

State Department spokeswoman Marie Harf declined to detail US efforts to secure the release of the three men, but said the offer to send King still stood.

But an unnamed US official has told Reuters that as long as North Korea imposes "unacceptable conditions", it is not possible for Washington to send a special emissary to Pyongyang.

Source: Agencies