POLICE are reportedly investigating the suspected gang rape of a woman after the attack was live-streamed on Facebook.

An online witness said the victim had her clothes pulled off by armed men and was sexually assaulted before cops arrived and turned off the camera.

4 Two of the alleged attackers pose with what looks like a revolver during the live-stream attack

4 This is reportedly the moment a police officer arrived at the scene and confronted the attackers

According to Swedish tabloid Aftonbladet, three people have been arrested after the alleged attack was broadcast in a closed Facebook group last night.

The horrific assault took place in an apartment in Uppsala, Sweden.

Police rushed to the scene after they were tipped off by someone watching the live stream in horror.

The victim was apparently close to unconscious as the she was assaulted.

Witness Josefine Lundgren, 21, called the police immediately when she tuned into the live footage.

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She told Sweden's Expressen: "He pulled her clothes off and lay on top of her."

A few hours later she saw a uniformed policeman interrupt broadcast as he arrived at the scene. He confronted the men and demanded they come to the station before shutting off the webcam.

Another person watching the stream told the paper: "I first thought it was a poorly orchestrated joke."

4 21-year-old Josefine Lundgren saw the live-stream and tipped off the cops

4 The attack reported took place in Uppsala, Sweden, near Stockholm Credit: Google

"The first thing you think is 'how can you do such a thing to a girl? And how can you do it live when you know that you are going to go there?'" a former member of the closed group told the Expressen.

"I think of course it is screwed, totally sick," they added.

Regional police have begun an investigation and the apartment is being examined by forensic scientists.