Several online viewers of the crime alerted police on Sunday, who then raided an apartment in the city of Uppsala and arrested the men aged 18 to 24, deputy chief prosecutor Magnus Berggren said.

Video extracts published on Swedish media showed the stream ending when police entered the apartment.

About 200 people were logged into the closed Facebook group during the assault, local media reported.

Josefine Lundgren, 21, who called police, told daily "Expressen" that a man "tore the clothes off" his victim before raping her.

The attacker also "filmed everything and took pictures that he put on [messaging site] Snapchat," she said.

A 22-year-old woman identified only as Lovisa, who was a member of the 60,000-member group, told Stockholm daily "Aftonbladet" she saw "two guys pressing down a girl on a bed, and touching her up. It looked like she was out of it."

Copies circulating the web

Berggren said police did not have a copy of the video showing the attack itself.

Police spokeswoman Lisa Sannervik urged people who had downloaded the video not to share it with others, but instead hand it to police investigators.

The video was removed from Facebook but copies had been circulated on the internet. Swedish media published excerpts from the video showing at least one of the suspects holding a revolver.

The suspects could face charges for streaming the attack, in addition to one of aggravated rape, Berggren said.

A press spokesman for Facebook in the Nordic countries denounced "a hideous crime."

"Our teams work around the clock to review content that is being reported by users" and Facebook cooperates systematically with police in criminal investigations, he told AFP.

Video part II

According to Sweden's state broadcaster SVT, the men also made a second live broadcast in which the suspected victim stated that she had not been raped. The broadcast was continuing as police arrived at the flat and arrested those present.

But there were questions raised about whether the woman had been coerced into issuing the denial.

"My heart broke," Linda Johansson, who saw the second of the broadcasts, told SVT. "The girl was sitting in front of the camera while the guy who filmed her tried to make her deny that she had been raped.

"He was putting the words in her mouth. He was extremely threatening and laughed throughout the film," Johansson said.

aw, jbh/cmk, se (AFP, dpa, Reuters)