N Korea releases CCTV footage of US student stealing banner

North Korea has released CCTV images showing American student Otto Warmbier removing a political banner from a wall in a hotel -- a "crime" that saw him sentenced to 15 years hard labour.

The brief CCTV clip, taken in a staff-only area of the Yanggakdo International Hotel in Pyongyang, was submitted as evidence during Warmbier's trial on Wednesday.

The United States has accused the North of using Warmbier as a political pawn and condemned the sentence as way out of proportion to what amounted to little more than a misdemeanour.

The grainy, black-and-white footage showed the 21-year-old student from the University of Virginia removing the metre-long, mounted poster from the wall and laying it on the ground.

The banner carried a slogan in bold white lettering on a red background. Part of the banner was blanked out at the trial, but it appeared to read: "Let us strongly arm ourselves with Kim Jong-il's patriotism."

The CCTV images, released late Thursday, did not show exactly what Warmbier did after taking it down, and it was unclear if he attempted to take the poster out of the country.

Warmbier was arrested at the airport as he was leaving the country with a tour group on January 2.

Four days later, North Korea conducted its fourth nuclear test and experts say the resulting surge in military tensions and the adoption of tough new UN sanctions were probably behind the harsh sentence.

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