A gunman has reportedly shot several people at the Mandalay Bay casino in Las Vegas

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People flee an area under police lockdown near the Mandalay Bay Casino in Las Vegas.

At least one gunman has shot several people, according to social media reports, and is still on the loose at the Manadalay Bay Casino in Las Vegas.

The shooter fired on at least two people around the casino-hotel, one of the major landmarks on the city's central strip.

Video posted by journalist Josh Caplan on Twitter appeared to show the moment that the sound of gunfire from an automatic weapon began at a country music concert outside the hotel. (Viewers may find parts distressing):

Photographs showing the concert area after most people had fled, which Business Insider is not republishing, showed at least one apparent victim covered in blood on the ground.

Twitter users citing local police scanners said that as many as two gunmen were later active inside the hotel, on the 32nd floor, according to the Reuters news agency. It is not clear whether they were the same person or people responsible for the gunfire outside.

The Las Vegas Police Department said it was "investigating reports of an active shooter" and told the public to stay away.