The U.S. State Department announced on Wednesday that a ban on travel by U.S. passport holders to North Korea will take effect on September 1.
Americans in North Korea should leave before that date while journalists and humanitarian workers may apply for exceptions to the ban, the department said in a public notice quoted by Reuters.
The ban comes a month after the U.S. government said it would bar Americans from traveling to North Korea due to the risk of "long-term detention" there.
In June, American student Otto Warmbier passed away after being held prisoner in North Korea for 17 months.
Warmbier suffered severe brain damage while in North Korean captivity. He was returned home to his parents while in a coma, where he later died.
The ban also comes at a time of heightened tensions between the United States and North Korea, which has been working to develop a nuclear-tipped missile capable of hitting the United States.
North Korea will become the only country to which Americans are banned from traveling, noted Reuters.
The State Department issued a notice in the Federal Register on Wednesday declaring U.S. passports invalid for travel to, in or through North Korea. The restriction takes effect in 30 days, and applies for one year unless extended or revoked by the secretary of state.
"Persons currently in North Korea on a U.S. passport should depart North Korea before the travel restriction enters into effect on Friday, September 1, 2017," the department said in a statement quoted by Reuters.
Professional reporters or journalists, representatives of the International Committee of the Red Cross or the American Red Cross traveling on official missions, those traveling to North Korea for "compelling humanitarian considerations" and those whose requests are "in the national interest" may ask for a special validation of their passports in order to travel to the country, the State Department said.
North Korea is still holding two Korean-American academics and a missionary, a Canadian pastor and three South Korean nationals who were doing missionary work, according to Reuters. Japan says North Korea has also detained at least several dozen of its nationals.
This past week, North Korea test-fired an intercontinental ballistic missile (ICBM), for the second time in less than a month.
On Monday, two American officials assessed, based on last week’s test, that North Korea's missiles may now be able to reach most of the continental United States.