Otto Warmbier, an American student who fell into a coma while imprisoned in a North Korean labour camp, has died.

Mr Warmbier, 22, was returned to the United States a week ago on a military plane after Pyongyang allowed him to be flown home.

He had been 17 months into a 15-year sentence, convicted of subversion after tearfully confessing that he had tried to steal a propaganda banner.

The University of Virginia student suffered severe brain damage while being held in North Korea but it was not clear what caused it.