American citizens will be banned from traveling to North Korea beginning at the end of August, the State Department announced Friday.

"Due to mounting concerns over the serious risk of arrest and long-term detention under North Korea's system of law enforcement, the Secretary has authorized a Geographical Travel Restriction on all U.S. citizen nationals' use of a passport to travel in, through, or to North Korea," spokeswoman Heather Nauert said in a statement.

When the ban goes into effect, U.S. travelers will need to obtain "special validation" from the State Department to legally travel to North Korea. Validation will be granted for "humanitarian" and other unspecified reasons.

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The State Department said it intends to publish a notice in the Federal Register next week. "The restriction will be implemented 30 days after publication of the Federal Register notice announcing the restriction," the statement said.

Young Pioneer Tours, the company with which American student Otto Warmbier traveled to North Korea, released a statement via Twitter on Friday morning, saying the ban would come into effect within 30 days of July 27.

#BREAKING Read statement regarding the US travel ban to DPRK here: https://t.co/UhZI3fc6K8 — Young Pioneer Tours (@YPioneerTours) July 21, 2017

"After the 30 day grace period any U.S. national that travels to North Korea will have their passport invalidated by their government," the Young Pioneer statement said.

According to the Reuters news agency, another tour operator which runs trips into North Korea, Koryo Tours, also said they had been told about the looming ban, adding that they did not know how long it would last.

Otto Warmbier, a 22-year-old American student at the University of Virginia, was medically evacuated after being freed by North Korea after having been sentenced to 15 years of hard labor. He was accused by the North Korean government of trying to steal a propaganda banner and was convicted of subversion.

The Trump administration began considering a ban on U.S. citizens traveling to North Korea after the death of Warmbier in a hospital after he was flown back home in coma.

Warmbeir's father lashed out after his son's death at the tour companies that arrange trips to the isolated totalitarian state. "The North Koreans lure Americans to travel to North Korea via tour groups run out of China who advertise slick ads on the internet," Fred Warmbier said.

Rep. Adam Schiff, a California Democrat and sponsor of the North Korea Travel Control Act, applauded the decision Friday.

"After the horrific treatment of Otto Warmbier, only the latest American detained by the regime, limiting U.S. travel is unfortunately sensible and necessary," Schiff said in a statement.

The State Department said in June that at least 16 Americans have been detained by North Korea during the last 10 years. A travel warning for U.S. nationals is already in place.