An American official has claimed that U.S. and South Korean special forces parachuted into North Korea to gather intelligence on Pyongyang’s apparent network of underground military facilities.

Speaking to a conference in Florida last week, Army Brigadier General Neil Tolley, commander of U.S. special forces in South Korea, said that the North Koreans have constructed thousands of tunnels since the end of the Korean war almost sixty years ago.

The entire tunnel infrastructure is hidden from our satellites, Tolley said. So we send [South Korean] soldiers and U.S. soldiers to the North to do special reconnaissance. After 50 years, we still don't know much about the capability and full extent of the underground facilities.”

It is unclear when these reconnaissance missions took place or if they are continuing.

Tolley added that at least four of the tunnels go under the Demilitarized Zone (DMZ) which separate North and South Korea.

However, a U.S. special forces spokesman in South Korea denied the allegations.

 No U.S. or [Republic of Korea] forces have parachuted into North Korea, he said.

Though special reconnaissance is a core special operations force mission, at no time have [Special Operations Forces] forces been sent to the north to conduct special reconnaissance.”

He added: The use of tunnels in North Korea is well documented. Several of the known tunnels along the DMZ are visited by tourists every day.