Large crowds flocked immediately to casinos such as The D, which had flown in gamblers from across the country on hundreds of free flights to boost the occasion.

"We're fired up... You can see the smiles on everybody's faces," owner Derek Stevens told journalists. "Everybody's just excited."

On the world-famous Strip, which has been almost deserted since mid-March, casinos and resort hotels began reopening more slowly after dawn.

The Bellagio's fountains were switched back on shortly before its sprawling casino floors reopened, as dozens of curious locals and excited tourists lined up to enter at 10 am.

The reopening is a major boost for the badly-hit Las Vegas economy, which depends heavily on tourism and has seen unemployment shoot as high as 33.5 percent in April.

Inside the city's gaming rooms -- capped at half capacity -- strict restrictions were in place, with blackjack tables limited to three players in order to maintain social distancing, and fitted with plexiglass barriers between players and dealers.

Staff were instructed to ensure crowds do not gather around players at craps tables, where a maximum six can stand at once. 

"Vegas is still Vegas," MGM Resorts CEO William Hornbuckle told AFP earlier.

"Over time, we'll get fully back," he added.

Read also: Wynn Resorts CEO calls for Las Vegas Strip to conditionally reopen in mid- to late May

Guidelines for the company, which operates the Bellagio, MGM Grand, New York-New York and other casinos, require every other slot machine to be switched off.

Guests are "strongly encouraged" to keep face coverings on while gambling, but drinks are once again being served on the casino floor.

At nearby Treasure Island, 29-year-old Alecia Perez had driven up from Los Angeles on Thursday morning with her partner and young child.

"We have a toddler so that's another reason we came now, we figured it'd be a little more empty," she told AFP.

"It's a different type of vacation -- we're not looking to party."

Nightclubs and giant Las Vegas shows remain closed for now. Many casinos are conducting temperature checks on entry.

"It's gonna be a little scary at first of course. I'm not going to make as much money as I usually do," said Luis Rosales, preparing for his first shift back working as a server at the Venetian hotel.

"But it's just going to take a little bit of time."

He added: "I get to go to the bars now, to go gambling. That's what we've all been missing."

As well as recovering from coronavirus, the city has been hit with tense protests over the death of George Floyd, an unarmed black man whose videotaped killing by police in Minnesota went viral and triggered demonstrations across the US.

A Las Vegas officer was in "grave condition" after being shot during protests earlier this week, and an armed Hispanic man was shot and killed by police after raising his gun in a separate, nearby incident.

Three far-right extremists were arrested and charged by anti-terror officials for inciting violence.