An attendee poses alien doll as an influx of tourists responding to a call to 'storm' Area 51 is expected

UFO enthusiasts began descending on rural Nevada on Thursday near the secret US military installation known as Area 51, long rumoured to house government secrets about alien life, with local authorities hoping the visitors were coming in peace.

Some residents of Rachel, a remote desert town of 50 people a short distance from the military base, worried their community might be overwhelmed by unruly crowds turning out in response to a recent, viral social-media invitation to "storm" Area 51. The town, about 150 miles (240 km) north of Las Vegas, lacks a grocery store or even a gasoline station.

Dozens of visitors began arriving outside Rachel's only business - an extraterrestrial-themed motel and restaurant called the Little A'Le'Inn - parking themselves in cars, tents and campers. A fire truck was stationed nearby.

One couple, Nicholas Bohen and Cayla McVey, both sporting UFO tattoos, travelled to Rachel from the Los Angeles suburb of Fullerton with enough food to last for a week of car-camping.

"It's evolved into a peaceful gathering, a sharing of life stories," McVey told Reuters, sizing up the crowd. "I think you are going to get a group of people that are prepared, respectful and they know what they getting themselves into."

Area 51 was shrouded in secrecy for decades, stoking conspiracy theories that it housed the remnants of a flying saucer and the bodies of its alien crew from the crash of an unidentified flying object in Roswell, New Mexico, in 1947. The US government did not confirm the base existed until 2013, when it released CIA archives saying the site was used to test top-secret spy planes.

The documents, however, did not end suspicion about space aliens there.

Rachel and its surroundings have long celebrated their place in UFO lore as a tourist draw. A 98-mile (158-km) road running through the area is dubbed the Extraterrestrial Highway, a purported hotbed of UFO sightings.

In June, California college student Matty Roberts posted a facetious Facebook invitation exhorting the public at large to run into Area 51 on foot to "see them aliens."

When more than 1 million people expressed interest, the U.S. Air Force admonished curiosity seekers not to breach the gates at the military base, which it said is still used to test combat aircraft and train personnel.

"No Stopping It"

Roberts then teamed up with Connie West, co-owner of the Little A'Le'Inn, to plan a music festival in Rachel dubbed "Alienstock" to entertain the expected crowds.

In early September, however, Roberts disassociated himself from the Rachel event, saying it was poorly organised and he feared it could devolve into a public safety crisis. Instead, he helped stage an alternative Alienstock set to take place Thursday night in Las Vegas. Beer brand Bud Light signed on as a sponsor and designed limited-edition, green beer cans featuring alien heads.

West said the event in Rachel would go on as planned.

"It's happening. There was no stopping it," she said on Thursday, adding that some visitors had come from as far away as Australia and New Zealand. "I hope they just enjoy the party we are throwing."

About 40 miles (64 km) east of Rachel, the small town of Hiko planned an event called "Storm Area 51 Basecamp" at a gift shop dubbed the Alien Research Center. Organizers promised musicians, artists and "prominent ufologists," and by Thursday had sold 3,200 tickets, according to Linda Looney, manager of the shop."This whole thing has been a shock to this little community," she said, adding that organizers had hired 15 security guards and a private ambulance and ordered 80 portable toilets. "It's going to be really cool. I'm excited."

The influx of alien hunters prompted Lincoln County, which encompasses Rachel and Hiko, to draft an emergency declaration that could be invoked if needed to call in help from the state.

The Lincoln County Sheriff's Office said visitors should expect "a large presence of law enforcement." Authorities urged everyone to bring ample supplies of food, water and fuel.

Five sheriff's patrol cars were posted just outside the Area 51 gate, where a handful of people had come to take photos.

Despite a festive, peaceful mood back in town, the official Rachel website was decidedly unwelcoming.

"If any event still happens it is going to be a pretty sad affair with no bands, no food, very little infrastructure and a lot of unhappy campers," it said.