An American student who admitted to stealing propaganda material from North Korea has been sentenced to 15 years hard labour for crimes against the state, China's official Xinhua news agency has reported.

The sentence was handed down on Otto Warmbier, a 21-year-old student from the University of Virginia, by North Korea's Supreme Court, Xinhua said in a brief despatch today.

There was no immediate confirmation of the sentence on North Korean state media.

Otto Warmbier bows his head in apology during a press conference last month. (AAP)

Mr Warmbier, who was arrested in early January as he was leaving the country, later said he had removed a political banner from the staff-only area of the Pyongyang hotel being used by his tour group.