An American college student who was released by North Korea in a coma has suffered a "severe neurological injury", a spokeswoman for the Ohio hospital treating him said.

People in the Ohio hometown of a college student released by North Korea said they are pleased he is back and expressed hopes for his recovery as he remained in a coma.

North Korea’s supreme court sentenced American student Otto Warmbier, who was arrested while visiting the country, to 15 years of hard labour for crimes against the state.

A US student held in North Korea since early January was detained for trying to steal an item bearing a propaganda slogan from his Pyongyang hotel and has confessed to “severe crimes” against the state, the North’s official media said.