Diplomatic tensions escalate as US man held after sneaking into North Korea

A US national is believed to have been taken into custody in North Korea while he was on a tour of the heavily guarded inter-Korea border without authorization, according to the United Nations Command.

The individual was touring the Joint Security Area (JSA), a border village in the Demilitarised Zone (DMZ) separating South Korea and North Korea where soldiers from both countries keep watch.

"A US national on a JSA orientation tour crossed, without authorization, the Military Demarcation Line into the Democratic People's Republic of Korea (DPRK)," the UN Command, which has assisted in DMZ supervision since the 1950–1953 Korean War armistice that put an end to hostilities, stated on Tuesday.

"We believe he is currently in DPRK custody and are working with our KPA counterparts to resolve this incident," it added, referring to the North Korean People's Army.

No further information about the individual or their reasons for crossing the border was provided.

The US Department of State and the South Korean Ministry of Defence made no immediate comments.

US citizens are prohibited from travelling to North Korea "due to the continuing serious risk of arrest and long-term detention of US nationals," according to the State Department's travel advisory, according to Al-Jazeera.

The ban was implemented after US college student Otto Warmbier was detained by North Korean authorities while on a tour of the country in 2015. 

He died in 2017, days after he was released from prison and returned to the United States in a coma.

It is uncommon for South Koreans or US citizens to defect to North Korea, but more than 30,000 North Koreans have fled their country since the end of the Korean War in order to escape political repression and economic hardship.