Otto Warmbier in North Korea
Otto Warmbier in North Korea Reuters

The United States on Wednesday accused North Korea of jailing an American student for political reasons and called for his immediate release, after Pyongyang sentenced him to 15 years' hard labor for stealing a propaganda sign from a hotel, AFP reports.

Otto Warmbier, a 21-year-old student from the University of Virginia, was convicted of subversive activities and sentenced by North Korea's Supreme Court, the North's official KCNA news agency said earlier.

In response, White House spokesman Josh Earnest charged that North Korea was using American citizens as "pawns to pursue a political agenda" and urged it to free him.

"We strongly encourage the North Korean government to pardon him and grant him special amnesty and immediate release," said Earnest.

"The allegations for which this individual was arrested and imprisoned would not give rise to arrest or imprisonment in the United States or in just about any other country in the world," he added, according to AFP.

Observers said the harsh sentence was likely a reflection of soaring military tensions on the divided Korean peninsula following the North's nuclear test in January and long-range rocket launch a month later.

In recent weeks Pyongyang has maintained a daily barrage of nuclear strike threats against both Seoul and Washington, ostensibly over ongoing large-scale South Korea-U.S. military drills that the North sees as provocative rehearsals for invasion.

In announcing the jail sentence, KCNA said Warmbier had committed his offense "pursuant to the U.S. government's hostile policy" towards North Korea.

Warmbier had initially been arrested in early January on charges of "hostile acts" against the state. KCNA said he was convicted under an article of the criminal code dealing with subversion.

In the past, North Korea has used the detention of American citizens to obtain high-profile visits from the likes of former presidents Jimmy Carter and Bill Clinton in order to secure their release.

Warmbier is one of three North Americans currently detained in North Korea, noted AFP, which recently sentenced a 60-year-old Canadian pastor to life imprisonment with hard labor on sedition charges.

Meanwhile on Wednesday, the Obama administration for the first time imposed sanctions on broad sectors of the North Korean economy, in response to its nuclear tests and threats.