A Sydney woman had her hair chopped off in a random attack on the bus.

A Sydney woman broke down after a couple sitting behind her on the bus began cutting off chunks of her hair.

Several witnesses saw the incident, which happened on the 339 bus between Clovelly and Sydney CBD this morning.

The couple, who were described as “creepy, freaky”, “did a runner” around Moore Park after other passengers began to notice what was happening.

The bus driver later tried to chase them when he spotted them in the street, but they escaped in a cab.

“She was really distressed,” a man who’d been sitting next to her told the Sydney Morning Herald anonymously.

“There was a good three or four inches cut off and she was obviously sure the guy had done it.”

The woman was in her early twenties and visibly upset when she began pulling loose bits of hair from her head, he said.

“I asked her if she wanted to move seats, and she said ‘no, it will be all right’ but once the couple got off the bus she completely broke down.”

He described the couple as “pasty and overweight”.

“The [woman] looked like she was drugged out of her head, Class-A whacked. She was completely off her tree.

“He was just so freaky. I had been reading a booklet on bicycle tracks in Perth and he tapped me on the shoulder and asked if he could have it when I had finished with it. It was such a weird request.”

“It was so creepy,” another passenger who was on the bus agreed, saying he’d noticed the couple immediately.

“She was sitting on his lap sucking her thumb. I thought ‘That’s a bit weird’. I moved so I wasn’t near them,” he said.

NSW Police are reportedly aware of the incident.