Fears that thousands of alien hunters could attempt to “storm” Area 51 after responding to a viral Facebook event have proved unfounded, with fewer than 200 people turning up at the gates of the secretive US military base.

Most of those left peacefully after "heated warnings" from police, although authorities said two people were arrested at perimeter of the remote facility in Nevada.

It was a far cry from the millions who signed up to Storm Area 51, a joke Facebook event which suggested attendees “all meet up” to “see them aliens” at the base which conspiracy theorists claim holds evidence of extraterrestrials.

The event page was later shut down following condemnation from American authorities and locals, who feared a “disaster” if huge crowds descended on the harsh desert area where internet, phone signal and credit card facilities are scarce.

But the invitation nonetheless spawned alien-themed festivals in the tiny Nevada towns of Rachel and Hiko nearest the military site.

Storm Area 51: Hundreds at US military base to 'see them aliens' Show all 40 1 /40 Storm Area 51: Hundreds at US military base to 'see them aliens' Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 Alien-hunters headed to Area 51 after a viral craze that saw them commit to storm the mysterious US military base as a variety of events are taking place to mark the weekend, including music festivals in a variety of locations Reuters Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 Martin Custodio wears a Pepe mask while standing near razor wire at an entrance to the Nevada Test and Training Range near Area 51 AP Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 A boy wears a tinfoil hat at the gates of Area 51 Reuters Storm Area 51: Hundreds at US military base to 'see them aliens' 'Alienstock' A man dressed as an alien dances at the 'Storm Area 51' spinoff event 'Alienstock Getty Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 A person carries a sign outside a gate to Area 51 as an influx of tourists responding to a call to 'storm' Area 51, a secretive U.S. military base believed by UFO enthusiasts to hold government secrets about extra-terrestrials, is expected in Rachel, Nevada, U.S. September 20, 2019. REUTERS/Jim Urquhart JIM URQUHART Reuters Storm Area 51: Hundreds at US military base to 'see them aliens' Rachel, Nevada Revelers pose at the 'Storm Area 51' spinoff event 'Alienstock' Getty Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 Alien-hunters gather to "storm" Area 51 at an entrance to the military facility near Rachel, Nevada AFP/Getty Storm Area 51: Hundreds at US military base to 'see them aliens' 'Alienstock' People dance during a DJ set at 'Alienstock' EPA Storm Area 51: Hundreds at US military base to 'see them aliens' 'Alienstock' Women dressed as aliens Getty Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 People holds signs at an entrance to the Nevada Test and Training Range near Area 51 Friday, Sept. 20, 2019, near Rachel, Nev. People gathered at the gate inspired by the "Storm Area 51" internet hoax. (AP Photo/John Locher) John Locher AP Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 A group of people take the "Naruto run" position before they faux ran at an entrance Reuters Storm Area 51: Hundreds at US military base to 'see them aliens' 'Alienstock' Audrie Clark smokes a vape outside of the Storm Area 51 Basecamp event AP Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 Attendee Ellie Urquhart walks past a security line AFP/Getty Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 A man poses at an entrance gate Getty Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 A mans holds an inflatable alien AP Storm Area 51: Hundreds at US military base to 'see them aliens' 'Alienstock' RACHEL, NEVADA - SEPTEMBER 20: Revelers gather at the 'Storm Area 51' spinoff event 'Alienstock' on September 20, 2019 in Rachel, Nevada. The event is a spinoff from the original 'Storm Area 51' Facebook event which jokingly encouraged participants to charge the famously secretive Area 51 military base in order to 'see them aliens'. Two tiny desert towns not far from from the once-secret Area 51 are hosting related events this weekend. The military has warned attendees not to approach the protected Area 51 military installation. (Photo by Mario Tama/Getty Images) Mario Tama Getty Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 A man poses for photos as attendees gather to "storm" Area 51 at an entrance to the military facility near Rachel, Nevada on September 20, 2019. (Photo by Bridget BENNETT / AFP)BRIDGET BENNETT/AFP/Getty Images BRIDGET BENNETT AFP/Getty Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 Alien-hunters gather to "storm" Area 51 at an entrance to the military facility near Rachel, Nevada on September 20, 2019. - Alien-hunters are arriving near Area 51 after a viral craze that saw them commit to storm the mysterious US military base as a variety of events are taking place to mark the weekend, including music festivals in a variety of locations. (Photo by Bridget BENNETT / AFP)BRIDGET BENNETT/AFP/Getty Images BRIDGET BENNETT AFP/Getty Storm Area 51: Hundreds at US military base to 'see them aliens' 'Alienstock' Hundreds gathered in Nevada desert to 'see them aliens' Getty Images Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 A military personnel member patrols with a dog Reuters Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 Alien-hunters discuss with law enforcement officers as they gather to "storm" Area 51 at an entrance to the military facility near Rachel, Nevada on September 20, 2019. - Alien-hunters are arriving near Area 51 after a viral craze that saw them commit to storm the mysterious US military base as a variety of events are taking place to mark the weekend, including music festivals in a variety of locations. (Photo by Bridget BENNETT / AFP)BRIDGET BENNETT/AFP/Getty Images BRIDGET BENNETT AFP/Getty Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 A person carries signs outside a gate to Area 51 as an influx of tourists responding to a call to 'storm' Area 51, a secretive U.S. military base believed by UFO enthusiasts to hold government secrets about extra-terrestrials, is expected in Rachel, Nevada, U.S. September 20, 2019. REUTERS/Jim Urquhart JIM URQUHART Reuters Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 A man poses in an alien costume near an access point to Area 51 EPA Storm Area 51: Hundreds at US military base to 'see them aliens' 'Alienstock' Attendees listen to music during Alienstock festival on the "Extraterrestrial Highway AFP/Getty Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 A security guard stands at an entrance AP Storm Area 51: Hundreds at US military base to 'see them aliens' 'Alienstock' People dance during a DJ set EPA Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 People dressed in costumes chant as they approach a gate to Area 51 Reuters Storm Area 51: Hundreds at US military base to 'see them aliens' 'Alienstock' RACHEL, NEVADA - SEPTEMBER 20: Revelers dance at the 'Storm Area 51' spinoff event 'Alienstock' on September 20, 2019 in Rachel, Nevada. The event is a spinoff from the original 'Storm Area 51' Facebook event which jokingly encouraged participants to charge the famously secretive Area 51 military base in order to 'see them aliens'. Two tiny desert towns not far from from the once-secret Area 51 are hosting related events this weekend. The military has warned attendees not to approach the protected Area 51 military installation. (Photo by Mario Tama/Getty Images) ***BESTPIX*** Mario Tama Getty Storm Area 51: Hundreds at US military base to 'see them aliens' epa07857665 Members of the public talk in front of the entrance of the Alien Research Center during a 'Storm Area 51' party organized in Hiko, Nevada, USA, 20 September 2019. Starting as a joke the 'Storm Area 51' transformed into a gathering for alien believer with music and attractions held in several places around the Area 51. EPA/ETIENNE LAURENT ETIENNE LAURENT EPA Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 A woman is detained by law enforcement after crossing into Area 51 Reuters Storm Area 51: Hundreds at US military base to 'see them aliens' A bus arrives for a 'Storm Area 51' spinoff event Getty Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 A man poses for photos as attendees gather to "storm" Area 51 AFP/Getty Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 An attendee wears a tinfoil hat Reuters Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 Danny Philippou, of Australia, pretends to "Naruto run" AP Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 epa07857873 People interact next to a military check point to Area 51 guarded by police officers and sheriff deputies as others go there to take pictures and possibly try to enter the site, near Rachel, Nevada, USA, 20 September 2019. Starting as a joke, the 'Storm Area 51' event transformed into a gathering for alien believers, with music and attractions held in several places around Area 51. EPA/ETIENNE LAURENT ETIENNE LAURENT EPA Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 Law enforcement monitor a gate to Area 51 Reuters Storm Area 51: Hundreds at US military base to 'see them aliens' 'Alienstock' People play with a football during a DJ set at 'Alienstock' EPA Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 People do the "Naruto run" at the gates of Area 51 Reuters Storm Area 51: Hundreds at US military base to 'see them aliens' Area 51 People celebrate on the road back after visiting a military security gate near Area 51 Getty Storm Area 51: Hundreds at US military base to 'see them aliens' 'Alienstock' Men dressed as aliens dance at the 'Storm Area 51' spinoff event Getty

Lincoln County Sheriff Kerry Lee estimated that about 1,500 people had gathered at the festival sites and said more than 150 people also made the rugged trip several additional miles on bone-rattling dirt roads to get within selfie distance of the gates.

Another group of about 40 people gathered at a different gate in the Amargosa Valley.

The military had issued stern warnings that lethal force could be used if people entered the Nevada Test and Training Range, and local and state officials said arrests would be made if people tried.

"It's public land," the sheriff said. "They're allowed to go to the gate, as long as they don't cross the boundary."

A music group called Wily Savage erected a stage on Thursday near the Little A'Le'Inn in Rachel and began playing after dark for several hundred campers who braved overnight temperatures about 7C.

Guitarist Alon Burton said: "It started as a joke, but it's not a joke for us. We know people will come out. We just don't know how many."

Daniel Martinez, 31, a Pokemon collectible cards dealer from Pomona, California, was among those dancing in the makeshift festival grounds.

"Here's a big open space for people to be," he said. "One person starts something and it infects everybody with positivity. Anything can happen if you give people a place to be."

The entertainment kicked off weekend events that also feature a gathering Friday and Saturday at the Alien Research Centre souvenir store in Hiko.

Owner George Harris said it would focus on music, movies and talks about extraterrestrial lore.

Authorities reported no serious incidents related to the festivals, which were scheduled to last until Sunday.

Hiko and Rachel are about a 45-minute drive apart on a state road dubbed the Extraterrestrial Highway, and a two-hour drive from Las Vegas.

Michael Ian Borer, a University of Nevada, Las Vegas, sociologist who researches pop culture and paranormal activity, called the festivities sparked by the internet joke "a perfect blend of interest in aliens and the supernatural, government conspiracies, and the desire to know what we don't know."

"People desire to be part of something, to be ahead of the curve," he said. "Area 51 is a place where normal, ordinary citizens can't go. When you tell people they can't do something, they just want to do it more."

Eric Holt, the Lincoln County emergency manager, said he believed authorities could handle 30,000 visitors at the two events. Still, neighbours braced for trouble after more than two million people responded to the "Storm Area 51" Facebook post weeks ago.

"Those that know what to expect camping in the desert are going to have a good time," said Joerg Arnu, a Rachel resident who can see the festival grounds from his home.

Those who show up in shorts and flip-flops will find no protection against "critters, snakes and scorpions," he warned.

"It will get cold at night. They're not going to find what they're looking for, and they are going to get angry," he added.