Police say they are questioning a man about an alleged attack on an elderly woman in Melbourne.

Officers say a taxi driver punched the 81-year-old woman in the face several times and pushed her out of a cab yesterday at Noble Park in the city's south-east.

The driver then pushed the woman out of the taxi and drove away.

The woman says she paid the driver up front before he took her in the wrong direction.

She says when she asked him to turn around, he pulled over, held down her seat belt so she could not move and punched her.

The woman's grandson, Syed, says she will never catch a taxi again.

"She's powerless. You can see she's 81 years old. Just for a little money, why would they do such a horrible thing?" he said.

"We escaped the Taliban, the war in Afghanistan, seeking peace and security in Australia.

"Luckily there is questioning and law and order here.

"We are happy there are people who will investigate this matter."

Victorian Taxi Association spokesman David Samuel says he has never heard of such an appalling incident before.

"We never accept physical confrontation from either side to be acceptable, and this sounds like that event occurring in the extreme," he said.

"We would tell anyone who witnessed this event to come forward and assist police in any way they can, be them a taxi driver or a member of the public.

"Certainly during my time at the Victorian Taxi Association, I have never heard of such an event occurring and it's certainly [something] we don't like to hear about and wouldn't like to hear about again."