HAIR-RAISING footage shows adventure bikers held at gunpoint by guards near the Area 51 site.

"Aggressive" armed gunmen confront the motorcyclists when they get too close to the infamous military base.

9 The bikers joke at the start of the video 'hey camo dudes we're back' and it's not long before the guards arrive Credit: YouTube / MacADVentures

9 The 'adventure tourists' have literally just got off their bikes before the guards patrolling the perimeter arrive all guns blazing Credit: YouTube / MacADVentures

9 Two guards emerge from the jeep in army fatigue and begin storming towards the bikers clearly armed Credit: YouTube / MacADVentures

9 The mystery gunmen are clearly in no mood for small talk and warn the bikers they will not 'ask again' when shouting instructions Credit: YouTube / MacADVentures

YouTubers MacADVentures decided to return after filming a similar incident four months ago.

"Hey camo dudes - we're back," they said at the start of video.

When heading towards the facility in Nevada they point to a valley known ominously as 'sniper hill'.

Military personnel with weapons patrol the perimeter of Area 51, with signs warning that security can use "deadly force".

The closely-guarded nature of Area 51 adds to the intrigue of a site long associated with UFO conspiracy theories.

RELATED STORIES PLANE SUSPICIOUS Area 51 mystery as unmarked jets spotted flying from Las Vegas to the top secret military base WHAT THE UFO IS THAT? Chinese rocket sparks alien invasion fears after burning up in sky over Area 51 OFF HIS ROCKET Aliens built space base on Earth 7,000 years ago and discovered PLUTO, minister claims Revealed Space invaders Pentagon officials are funding a secretive UFO-hunting operation... in the heart of London Video ALIEN BOUNTY HUNTER Meet the alien hunter who has spent his life chasing UFOs along America's 'paranormal highway'

When the two bikers stop at what's described as Area 51's secret back gate, they are confronted by the 'camo dudes'.

Panic sets in when the two guards, dressed in camoflauge, jump from their jeep.

They begin to reach for their guns, charging towards the men.

One of the guards said: "Put you're f***ing hands up, I'm not gonna tell you again."

9 'What are you doing all the way out here?' barks one of the guards as the bikers are ordered to put their hands up Credit: YouTube / MacADVentures

9 Towards the end of the video, one of the bikers remarked on the aggressive nature of the guard who 'kicked their legs apart' Credit: YouTube / MacADVentures

9 The tense footage shows the guards frisking and searching the bikers filming for their YouTube channel Credit: YouTube / MacADVentures

9 Signs warns that guards can use 'deadly force' if the trespassers do not leave when told Credit: YouTube / MacADVentures

The guards frisk and search the terrified bikers asking them what they are "doing all the way out here?"

One of the bikers replies: "We're adventure tourist.

"We are just planning on going back to Little Alien (an alien-themed travel complex nearby)."

The tense stand off is quickly over when the 'camo dudes' decide to let them leave.

One warns the bikers: "We're gonna give you a chance. Get on your bikes and get the f***k out of here or we'll get on the phone and call Lincoln County who'll write you a $700 ticket."

9 One of the warning signs for Area 51 clearly stating that photography is not allowed Credit: Alamy

The frightened bikers apologise for the "hassle" and turn round driving back down the track.

"That was crazy, they were so aggressive," said the biker as he leaves.

The US Air Force Base, around 80 miles from Las Vegas, is thought to be used for the development and testing of experimental aircraft.

The CIA only acknowledged it existed in 2013 after a Freedom of Information request.

Many conspiracy theorists claim that the base has been used for reverse engineering of an alleged crashed alien spacecraft at Roswell.

We pay for your stories! Do you have a story for The Sun Online news team? Email us at tips@the-sun.co.uk or call 0207 782 4368