Media playback is unsupported on your device Media caption Some alien enthusiasts attend 'Storm Area 51' event

Fears that thousands of people could storm Area 51 on Friday were unfounded, with just several dozen arriving at the secretive US military base.

Millions had responded to a Facebook post in June calling for people to raid the facility in Nevada on 20 September to "see them aliens".

But nobody attempted to enter the site and only one person was arrested - for urinating near the gate.

Area 51 has long been rumoured to house secrets about extraterrestrial life.

Image copyright Reuters Image caption None of the 75 people who turned up for the event attempted to storm Area 51

Why are people talking about Area 51?

In June, Matty Roberts, a student from California, posted a tongue-in-cheek Facebook event inviting people to charge at the base in large enough numbers to bypass security.

Within days of its launch, the event became a viral sensation, making headlines across the world. More than three million people expressed an interest in taking part.

However, warning signs around Area 51 made it clear that no trespassers would be tolerated.

Image copyright Reuters Image caption Little is known about what happens inside the facility

The US Air Force warned that Area 51 was "an open training range for the US Air Force, and we would discourage anyone from trying to come into the area where we train American armed forces".

What happened on Friday?

Not a lot.

Despite much anticipation surrounding the event, only around 75 people turned up at the front gate and nobody attempted to enter.

The only person to be arrested was a man caught urinating near the entrance and a woman was detained for an undisclosed reason, Associated Press reported.

The "raid" was more of a small-scale celebration, with enthusiasts dressing up and holding placards.

"I'm a little disappointed because it's a lot less people than they said online," Nathan Brown, who drove more than 700 miles from Portland, told the Las Vegas Review-Journal newspaper.

What is Area 51?

It was created during the Cold War between the US and the Soviet Union as a testing and development facility for aircraft.

Image copyright Getty Images Image caption Some local businesses have embraced Area 51's association with alien mythology

The secrecy surrounding the site has helped fuel many conspiracy theories.

Most famous is the claim that the site hosts an alien spacecraft and the bodies of its pilots after they crashed at Roswell, New Mexico, in 1947. The US government says there were no aliens and the crashed craft was a weather balloon.

Others claim to have seen UFOs above or near the site, while some say they have been abducted by aliens, and even experimented on, before being returned to Earth.