Police have said "one suspect is down" after a mass shooting in Las Vegas.

But they urged people to continue to avoid to Nevada city's famous gaming strip amid fears of further shooters.

"Confirming that one suspect is down," tweeted Las Vegas Metropolitan Police Department. "This is an active investigation. Again, please do not head down to the Strip at this time."

Police later added: "At this time we do not believe there are any more shooters."

At least two people have been killed and 24 injured after a gunman opened fire at a country music festival near the Mandalay Bay Hotel and Casino.

Witnesses reported seeing muzzle flashes from the upper floors of the hotel towards crowds at Route 91 Harvest country music festival.

Two festival-goers reporting hearing a noise "like firecrackers" before realising a shooter or shooters were unloading "clip after clip" into the crowd.

Reports on social media, citing police scanners, said the suspect was found on the hotel's 32nd floor.

Officers carrying assault rifles were seen running into the hotel, while others took cover behind vehicles.

Police have placed the area on lockdown and closed off parts of the Las Vegas Strip and Interstate 15.

Police urged people not to "livestream or share tactical positions of our officers on scene."