A man claiming to have a gun is barricaded in a hotel room at Caesars Palace, holding a woman against her will, and chucking large items through a window ... and now, SWAT's on the scene.

Cops say this started Tuesday morning with a call for possible domestic violence at the famed casino resort. When officers arrived, they say the man bolted into a room as they were trying to make contact -- he told them he wasn't coming out. Not just that, but he said he was armed.

BTW, Metro PD says he's not in there by himself ... the guy yanked a woman into the room with him before things went south -- and now, he's shattered windows as he throws items out of his room ... which is on a high floor. One reported object that's come down is a chair.

The authorities are telling people to clear the area or to take cover ... and there are videos and photos circulating online showing guests and passersby doing just that, hiding in fear.

Considering the man might have a weapon on him, and could start firing out the windows ... the police have called in SWAT officers who are getting into position throughout the area. A crisis negotiating team is also on site.

Police say no shots have been fired yet.

Of course, what comes to mind here is the 2017 Las Vegas massacre ... where Stephen Paddock opened fire from a hotel room in the Mandalay Bay Hotel during a music festival, killing dozens of people and injuring hundreds of others.