Las Vegas police have said there are "in excess of 50 dead" and more than 200 injured after a mass shooting at a music festival.

Clark County Sheriff Joseph Lombardo also confirmed the main suspect in the attack, the deadliest shooting in US history, was 64-year-old Stephen Paddock.

The gunman opened fire on crowds at Route 91 Harvest country music festival on the Nevada city's famous strip from the 32nd floor of a nearby hotel.

He was later shot dead by police and officers used explosives to burst into his hotel room and confront him.

The death toll, which police warned could rise, surpassed the 49 people shot dead at an Orlando nightclub in June last year.

Mr Lombardo said several firearms were found in Paddock's hotel room at the Mandalay Bay Hotel and Casino, across the street from the festival. Officers are also set to begin searching his home address.

The gunman's motive was unclear, added Mr Lombardo.

He added police were "confident" they have located a woman who lived with Paddock who authorities had said was a "person of interest".

Stephen Paddock: Las Vegas gunman identified by police as 64-year-old white male

Police earlier said said Marilou Danley, 62, was "sought for questioning" in connection to the shooting.

Thousands of panicked festival-goers fled as hundreds of shots rained down upon the crowd, with some people trampled on amid the chaos.

Two off-duty police officers who had attended to concert were believed to be among the dead.

Las Vegas's casinos and nightlife draw 3.5 million visitors a year from around the world the strip was packed with people when shooting broke out during a performance by country star Jason Aldean.

Las Vegas shooting – in pictures Show all 15 1 /15 Las Vegas shooting – in pictures Las Vegas shooting – in pictures People scramble for shelter at the Route 91 Harvest country music festival after gun fire was heard Getty Las Vegas shooting – in pictures People carry a person at the Route 91 Harvest country music festival after shots were fired David Becker/Getty Las Vegas shooting – in pictures People run from the Route 91 Harvest country music festival after gun fire was heard David Becker/Getty Las Vegas shooting – in pictures A handout photo released via Twitter by Eiki Hrafnsson (@EirikurH) showing concertgoers running away from the scene (C) after shots range out at the Route 91 Harvest festival on Las Vegas Boulevard EPA/Eiki Hrafnsson Las Vegas shooting – in pictures People lie on the ground at the Route 91 Harvest country music festival after hearing gun fire Getty Las Vegas shooting – in pictures A man in a wheelchair is taken away from the Route 91 Harvest country music festival after hearing gun fire David Becker/Getty Las Vegas shooting – in pictures People stand on the street outside the Mandalay Bay hotel near the scene of the Route 91 Harvest festival on Las Vegas Boulevard EPA/Paul Buck Las Vegas shooting – in pictures FBI agents confer in front of the Tropicana hotel-casino after a mass shooting during a music festival on the Las Vegas Strip Reuters/Las Vegas Sun/Steve Marcus Las Vegas shooting – in pictures Las Vegas police run by a banner on the fence at the Route 91 Harvest country music festival grounds after shots were fired David Becker/Getty Las Vegas shooting – in pictures An injured person is tended to in the intersection of Tropicana Ave. and Las Vegas Boulevard after a mass shooting at a country music festival Ethan Miller/Getty Las Vegas shooting – in pictures Metro Police officers pass by the front of the Tropicana hotel-casino after a mass shooting at a music festival on the Las Vegas Strip Reuters/Las Vegas Sun/Steve Marcus Las Vegas shooting – in pictures A woman sits on a curb at the scene of a shooting outside of a music festival along the Las Vegas Strip AP/John Locher Las Vegas shooting – in pictures A cowboy hat lays in the street after shots were fired near a country music festival in Las Vegas Getty Las Vegas shooting – in pictures Las Vegas Metro Police and medical workers stage in the intersection of Tropicana Avenue and Las Vegas Boulevard South after a mass shooting at a music festival on the Las Vegas Strip Reuters/Las Vegas Sun/Steve Marcus Las Vegas shooting – in pictures Sheriff Joe Lombardo (2-R) speaking during a press briefing in the aftermath of the active shooter incident on Las Vegas Boulevard EPA

Shocked concert-goers, some with blood on their clothes, wandered the streets after the attack. Some were trampled on in the panic to escape the festival venue.

The suspect was a local Las Vegas man who acted alone and was not believed to be connected to any militant group, Sheriff Lombardo said.

"We have no idea what his belief system was," he added. "Right now, we believe he was the sole aggressor and the scene is static."

Video of the shooting showed Aldean stopping mid-song after gunfire could was heard.

The gunman then fired another volley, with muzzle flashes visible at the hotel as more victims fell to the ground and others fled in panic.

Some festival-goers hid behind merchandise and food stands and other crawled under parked cars.

Marilou Danley: Las Vegas police statement on female roommate of gunman Stephen Paddock

Jake Owen, a country music star who played the set before Aldean, said "gun shots were ringing off of the stage rigging and road cases. No one knew where to go."

Witness Kodiak Yazzie, 36, said the music stopped temporarily when the first shots began. He said the song resumed, before the second round of pops sent performers ducking for cover and fleeing the stage.

"It was the craziest stuff I've ever seen in my entire life," Mr Yazzie said.

"You could hear that the noise was coming from west of us, from Mandalay Bay. You could see a flash, flash, flash, flash."

British tennis player Laura Robson was among those attending the concert.

She shared two pictures of herself at the event, wearing a cowboy hat with an American flag emblazoned on it.

Asked by a Twitter follower if she was all right, she wrote: "I'm okay. We were right there... sounded like fireworks at first then everyone started running."

She described the scenes as "scary".

Witnesses said the gunfire lasted for about five months.

"It sounded like fireworks. People were just dropping to the ground. It just kept going on," said Steve Smith, a 45-year-old visitor from Phoenix, Arizona, who had flown in for the concert.

He added: "Probably 100 shots at a time. It would sound like it was reloading and then it would go again. People were shot and trying to get out. A lot of people were shot."

Mike McGarry, 53, from Philadelphia, was at the concert with his children. He attempted to shield them from gunfire and and was trampled on as people fled in panic.

"It was crazy. I laid on top of the kids. They're 20. I'm 53. I lived a good life," he said.

The shooting broke out on the final night of the three-day festival, a sold-out event attended by thousands and featuring top country acts such as Eric Church, Sam Hunt and Jason Aldean.