Police said that the shooter was taken "down" after officers swarmed over the famous boulevard following reports of multiple shots being fired from the Mandalay Bay casino.
"At this time we do have a suspect down," Las Vegas police officer Steve Gomez told reporters, without elaborating. "We have numerous victims right now," he added.
While police did not immediately give a figure for the number of dead, CNN reported that at least two people had been killed in the shooting while several local news outlets put the number of injured at up to 24.
Pictures taken at the scene showed revelers cowering in the street or running in terror, as well what appeared to be several bodies lying prone on the ground.
A local hospital was taking in "several" people with gunshot wounds, University Medical Centre spokeswoman Danita Cohen told the local Sun newspaper.
Video footage circulating on social media purportedly of the Mandalay Bay showed a crowd enjoying a country music concert before what sounded like volleys of automatic gunfire halted the performance.
A witness told local TV news station KLAS he saw someone several stories high firing hundreds of shots into a crowd of people.
Police however denied reports of multiple shooters.
"At this time we do not believe there are any more shooters," the department wrote on Twitter.By Vietnamnews.