Las Vegas police are investigating reports of shooting incidents at other venues on the strip, after at least one gunman opened fire on a music festival next to the Mandalay Bay casino.
Police said a suspect was shot dead and they did not believe there was another shooter "at this time".
At least 20 people were killed and more than 100 injured in the mass shooting at the country music event.
Apparent automatic gunfire rang out in footage of the incident, which showed terrified concert-goers fleeing the scene.
Kodiak Yazzie, a 36-year-old attending the Route 91 festival, told Associated Press he heard what sounded like fireworks while he was watching US country musician Jason Aldean's performancee.
He said the music stopped, but then started up again before another round of pops prompted the performers to duck for cover and flee the stage.
As the 40,000 fans in the crowd began to run away, Mr Yazzie took cover and said he saw flashes of light coming from the Mandalay Bay hotel tower.
The bursts of pops would start and stop for more than five minutes.
Flights at McCarran International Airport were temporarily halted, the airport said on Twitter.
Agencies contributed to this report
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