A new documentary about the Femen topless activists shown in Venice on Wednesday reveals a little-known detail -- their feminist group was founded by a man.

The film explores the internal divisions within the Ukrainian group over the guru-like and secretive figure of Victor Svyatski, who is no longer a member.

Femen have drawn attention worldwide with nude stunts targeting a range of political and religious figures, including Silvio Berlusconi and Vladimir Putin.

"Ukraine Is Not a Brothel" by Australia's Kitty Green screened at the Venice film festival just days after the women's power organisation announced it was leaving Ukraine because of police intimidation.

Six of the activists briefly bared their breasts in Venice and later spoke to AFP with T-shirts back on.

Inna Shevchenko, a green-eyed blonde and one of the current leaders of the group, said Svyatski had a "grip" on Femen and forced many women members to quit.

Shevchenko, who inspired the design of a French postage stamp depicting cultural symbol Marianne, said Svyatski's "patriarchal" ways gave the real feminists in the organisation something to react against.

Svyatski "helped us understand how men can be bastards".

"Without this patriarchal world in which we grew up and which we want to escape, we would maybe not have had the courage to build this movement," she said.

Shevchenko said she had left Ukraine a few days ago.

"We are happy to be able to talk to you and to find ourselves in a safe place," she said.

She accused Ukrainian politicians and the secret service of "trying to attack us violently".

The founders of Femen decided to leave when they were called in by police for questioning last week after a gun and a hand grenade were found during a raid by security forces on Femen's offices in Kiev.

Femen were founded in Ukraine in 2008 and first drew international attention by destroying Ukrainian Orthodox crucifixes. Their main office is in Paris.

Their nude protests on a range of themes from sexism to various forms of discrimination to authoritarianism -- have drawn praise but have also caused deep offence and are sometimes dismissed as lacking true meaning.

Green spent several months following the lives and demonstrations of Femen activists.

"I filmed more than a hundred protests. I was arrested probably seven or eight times at protests," she said.

"I was abducted by the KGB and deported from Belarus at one stage. But I got used to getting arrested by the end I was okay with it. But at the start it was very scary," she added.

Green said that at the beginning she thought about abandoning her project because of Svyatski's role.

"After few months I learned the truth about the movement and what's going on and how it is run and I was a bit disappointed. I didn't really believe they where feminists for a while," she said.

"I had to choose whether I keep making my film or go home and just forget about them because I didn't agree. And I decided that I was gonna stay and expose the truth and show the real organisation," she added.

"Hopefully the girls can move forward from this."

Sasha Shevchenko, another Femen activist who is no relation to Inna, said: "Our body belongs to us, and more and more women are daring to live it, including in the Muslim world"