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The ugly attack terrified the women, who were singing in French after returning from a Remembrance Day barbecue at the beach before catching the Frankston bus late on November 11.
They were threatened with filleting by fishing knife, one was called a c*** and a dog, and an Australian woman passenger told her to "speak English or die".
"I thought [the man who began the abuse] was kind of joking at first and then I realised he wasn't kidding at all, so my friends and I stopped laughing" one of the group, Fanny Desaintjores, told the Age.
"We were quite afraid that he would come and hit us."
The YouTube video, posted by fellow passenger Mike Nayna, has gone viral and has been picked up by the international media, including reports of Australian "xenophobia" in France.
The incident began as an apparently drunk passenger objected to about nine women singing in French.
"One girl started singing in French and a girl up the front started telling her to shut up and chanted 'Aussie, Aussie, Aussie'," Nayna told the Herald Sun.
"Most at the front of the bus joined in, and that's when the passenger in the video on his phone joined in the abuse."
Nayna said young men in the front of the bus egged him on.
"They gave him a beer and a smoke and even offered him a fishing knife, and then he went off saying 'I'll fillet these c***s'," he said.
"The French girl started to sing louder and they didn't like that so the started the 'f*** off to your own country' type of thing."
A couple with a baby in a pram joined in, with the man shouting: "I'll f***ing boxcutter you right now dog."
Desaintjores told the Age that as the couple left the bus the man smashed a window near them, knocking glass fragments on to her and a friend.
"At this point I was really scared," she said.
"I realise that maybe we shouldn't sing in a public transport but I think that's insane that they reacted like that.
"We're all adults. We could have a conversation and talk gently, instead of all these insults and threats."
Police said the incident was being investigated by transit and public safety command detectives.