North Korea has sentenced a US citizen to 15 years of hard labour for crimes against the state.

State news agency KCNA, said Pae Jun-ho, who is known in the US as Kenneth Bae, was tried on 30 April in the Supreme Court.

He was arrested in November last year after entering North Korea as a tourist.

Mr Bae was arrested in Rason, a special economic zone in North Korea's far northeastern region bordering China and Russia.

The exact nature of Mr Bae's alleged crimes has not been revealed.

The development further complicates already strained ties between North Korea and the US.

The sentencing of Mr Bae, described by friends as a devout Christian and a tour operator, comes amid signs of tentative diplomacy following weeks of rising tension in the region.

North Korea had been warning of nuclear war and missile strikes in response to UN sanctions.

The sanctions were imposed after a long-range rocket launch in December and a nuclear test in February.

Analysts say North Korea could use Mr Bae as a bargaining chip as it seeks dialogue with the US.

The US State Department has not commented on the sentencing.

It is not the first time a US citizen has been arrested and sentenced to hard labour during a nuclear standoff.

In 2009, after the launch of an earlier long-range rocket and a second underground nuclear test, two US journalists were sentenced to 12 years of hard labour after sneaking across the border from China.

They later were pardoned on humanitarian grounds and released to former US President Bill Clinton, who flew to Pyongyang on a rescue mission.

He also met with then-leader Kim Jong-Il, which paved the way for talks.