The US has ended visa-free entry for tourists who have visited North Korea since 2011.
Currently, citizens of 38 countries - including South Korea, Japan and France – are able to enter for up to 90 days without a visa under a waiver programme.
But a new move from Washington on Monday means that visitors who have travelled to eight countries including North Korea are "no longer eligible", and they will have to apply for tourist or business visas.
The other seven countries - Iran, Iraq, Sudan, Syria, Libya, Somalia and Yemen - were already on the exclusion list.
The change will affect tens of thousands of people from visa waiver countries who have gone to the North as tourists or for other purposes in recent years.
US citizens have been banned from visiting North Korea since 2017, a measure introduced after an American student detained in Pyongyang was released in a coma and died a few days later.
The move will also put a damper on South Korean President Moon Jae-in's hopes of promoting cross-border tourism projects for his citizens to visit their nuclear-armed neighbour.
It comes despite improving relations between the US and North Korea, with Donald Trump becoming the first US President to step into North Korea.
