LAS VEGAS (NYTIMES, REUTERS) - Almost 60 people were dead and 515 injured when a gunman went on a shooting spree at a concert on the famous Las Vegas Strip late Sunday (Oct 1), raining down rapid fire from the 32nd floor of a hotel for several minutes before killing himself, in what has become the deadliest mass shooting in US history.

The shooting, identified as local resident Stephen Paddock, 64, killed himself before police arrived, and more than 10 guns were later found in his hotel room from where he carried out the attack, Las Vegas Metro Police Sheriff Joseph Lombardo said. He is believed to have checked into the room last Thursday, police said.

The death toll, which police emphasised was preliminary, would make the shooting the deadliest mass shooting in US history, eclipsing last year's massacre of 49 people at an Orlando night club by a gunman who pledged allegiance to the Islamic State in Iraq and Syria militant group.

Paddock was not believed to be connected to any militant group, Lombardo told reporters. "We have no idea what his belief system was," Lombardo said.

The Islamic State in Iraq and Syria (ISIS) later claimed responsibility for the attack, claiming that the suspect had converted to Islam "months ago", the group's news agency Amaq said, but US officials on the scene said they found no connection to international terrorist groups.

Authorities had earlier regarded Paddock's roommate Marilou Danley as a person of interest, but later on Monday said they no longer regarded her as related to the case, CNN and Fox News reported, citing police sources.

Some 22,000 people were in the crowd when the man opened fire, sending panicked people fleeing the scene, in some cases trampling one another, as law enforcement officers scrambled to locate and kill the gunman.

Shocked concertgoers, some with blood on their clothes, wandered the streets after the attack. At least 406 people were taken to area hospitals with injuries, the Las Vegas Metropolitan Police said.

Witnesses on social media said the shooting broke out on the last night of the three-day Route 91 Harvest festival, a sold-out event attended by thousands and featuring top acts such as Eric Church, Sam Hunt and best-selling country singer Jason Aldean.

US media, including Fox News, reported that Aldean was performing around 10.45pm local time on Sunday when the rampage began but that he had been bundled safely off stage at the event outside the Mandalay Bay Resort and Casino in the Nevada gambling mecca. CNN reported all the artists were safe.

Video posted online showed a musician performing outside the Mandalay Bay at Route 91 Harvest when the sound of automatic gunfire rang out. The music stopped, and concertgoers ducked for cover. "Get down," one shouted. "Stay down," screamed another.

Thousands of panicked people fled the scene, in some cases trampling one another as law enforcement officers scrambled to locate and kill the gunman. Shocked concertgoers, some with blood on their clothes, wandered the streets after the attack.

The dead included one off-duty police officer, Lombardo said. Two on-duty officers were injured, including one who was in stable condition after surgery and one who sustained minor injuries, Lombardo said. Police warned the death toll may rise.

'Like firecrackers'

"We were watching the concert having a great time, then we heard what sounded like firecrackers," witness Joe Pitz told the local Las Vegas Sun news outlet. "I guess it was an automatic weapon going off but it literally sounded like firecrackers.

"Then soon enough there was commotion on the Mandalay Bay side of the stage. They were motioning for medics to come and safety people to come and Jason Aldean ran off the stage. "Everybody in the vicinity went down. I don't know if they were ducking or if they were but it was chaos."

Another witness told local TV news station KLAS that he saw someone several stories high firing hundreds of shots into a crowd of people.

Several Swat teams were sent to the hotel, and officers reported being pinned down by gunfire, according to emergency radio traffic. The police also descended on the Ali Baba Restaurant, about a 10-minute drive from the Mandalay Bay, and they were also investigating reports of a shooting at the New York-New York Hotel and Casino.

The police reported clearing out the Mandalay Bay's 29th floor and working their way up to the 32nd floor. A Twitter post from the Las Vegas Police Department described reports of an "active shooter" near or around the Mandalay Bay casino.

The police reported closing off about a mile of Las Vegas Boulevard and asked the public to steer clear of the area.

Multiple flights were diverted away from Los Angeles' McCarran Airport due to the shooting.

Witnesses heard numerous gunshots at the casino hotel, where police tactical teams were searching for the attacker, according to reports on CNN and in the New York Times.

Another Twitter user, @mmmullen, wrote: "Active shooter outside my window Mandalay Bay, Las Vegas. Firing at outdoor concert. Long bursts of fully auto weapons."

The suspected shooter's brother, Eric Paddock, said the family was stunned by the news. "We have no idea. We're horrified. We're bewildered and our condolences go out to the victims," Eric Paddock said in a brief telephone interview, his voice trembling.

"We have no idea in the world."