The United States will bar Americans from travelling to North Korea in the coming weeks, two travel agencies said Friday, a month after US student Otto Warmbier died following his imprisonment by the Stalinist regime.

China-based Young Pioneer Tours, which had taken Warmbier to North Korea, and Koryo Tours said the ban will come into force on July 27 -- the anniversary of the end of the Korean War -- with a 30-day grace period.