North Korea says it has sentenced a U.S. citizen to 15 years of hard labor, BBC News reported.

The announcement, from state news agency KCNA, said Pae Jun-ho, known in the U.S. as Kenneth Bae, was tried on 30 April. He was held last year after entering North Korea as a tourist. Pyongyang said he was accused of anti-government crimes.

The move comes amid high tensions between North Korea and the U.S., after Pyongyang's third nuclear test.

North Korean media said last week that Pae had admitted charges of crimes against North Korea, including attempting to overthrow the government.

"The Supreme Court sentenced him to 15 years of compulsory labor for this crime," KCNA said.

Pae, 44, was arrested in November as he entered the northeastern port city of Rason, a special economic zone near North Korea's border with China. He is believed to be a tour operator of Korean descent.

"We call on the DPRK [North Korea] to release Kenneth Bae immediately on humanitarian grounds," U.S. State Department spokesman Patrick Ventrell said

North Korea has arrested several U.S. citizens in recent years, including journalists and Christians accused of proselytism. They were released after intervention from high-profile American figures, including former Presidents Bill Clinton and Jimmy Carter, both of whom went to Pyongyang.

In 2009, Mr Clinton negotiated the release of two U.S. journalists accused of entering North Korea illegally, Laura Ling and Euna Lee. Held after North Korea's second nuclear test, both had been sentenced to 12 years of hard labor before they were released.

Observers suggest Pyongyang could be using the jailed American as leverage, amid a very tense situation on the Korean peninsula.