A person wearing a disturbing clown mask has boarded a train in Melbourne, Australia, and terrified commuters.

A passenger, known only by the name of Karen, called 774 ABC Radio on Tuesday morning to complain about her experience travelling from Ballarat to Southern Cross station on Saturday morning.

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"I sat back expecting the usual relaxing trip ... when I got to Ardeer or Deer Park station a creepy looking guy got on the train wearing a suit. He appeared to be a young man, wearing an angry clown mask and carrying a suitcase."

She told the radio station she was shocked no one stopped the man, who looked like he had stepped off the set of a horror movie, from boarding the train. Then her journey took a turn for the worse.

Karen noticed from the shocked faces of those in front of her that the man dressed as a clown had walked from the third carriage to behind where she was sitting in the first carriage. He walked slowly to the front, turned around and "starred us all down."

"This is pretty creepy, all these things are running through your mind, it was pretty scary," Karen said. "Various scenarios [went through my mind]: What do I do? what does he have in the bag? What do I do if he pulls out a gun?"

She said his appearance was "menacing towards young females," as he slowly left the train and wandered around acting bizarrely. "The strange part was he was never pulled up, no one stopped him," Karen said.

After the story aired, a man named Andrew called into the same station on Tuesday afternoon, claiming the clown was in fact his step son. He said the 14-year-old would be getting a stern talking to for his antics on the train, and that he was on his way to his clowning class at the National Institute of Circus Arts Australia.

"On the weekend he is working on his different clown personas and costumes," Andrew said. "I knew he had that mask, but I did not know he was wearing it on the train. I will be giving him a talking to."

"He is only 14, so he probably didn't realise the impact he was having on people," he stressed.

Colin Tyrus, a spokesperson for the company that runs the trains, V-Line, said the train's conductor had investigated reports of a masked man, but said it appeared he was "just minding his own business."

"There was no threat that the conductor could perceive from this particular gentleman," Tyrus told ABC radio. "People might have, I think it's called coulrophobia, a fear of clowns."

He said there were no regulations to stop the wearing of masks on public transport, but that there is an emergency button in every carriage if people are concerned about their safety.

"We often have, actually, people with masks travelling on trains; in fact, I got on a metro train the other weekend and there were a few zombies on board," he said. The V-Line staff are trained to call police if anyone is being disruptive or threatening, Tyrus added.