Three women aged in their 70s and 80s have serious injuries after being pushed onto train tracks in Melbourne's south-east by a knife-wielding man.

The attack was recorded on security cameras.

Police said a 46-year-old Carnegie man got off a city-bound train at Glenhuntly station about 11:00am on Sunday carrying a kitchen knife.

He stabbed a woman's handbag, causing the knife to break, before he attacked five women.

Sergeant Jason Venturoni, of Victoria Police, said three of the victims, two of them aged 81 and 75, were pushed onto the tracks and taken to hospital with serious but non-life-threatening injuries.

"There are suspected fractures, possible hip fractures and head injuries," he said.

"Four of the five victims fell on to the tracks after being assaulted by the male, pushed or punched."

He said it was lucky no-one was killed.

"It was a very very serious incident and it could've resulted in the death of these ladies," he said.

Two other women, aged 25 and 36, suffered minor injuries.

Four women were pushed onto the tracks at Glenhuntly station. ( ABC News )

'I hid near the rubbish bin'

One of the women, Kelly Wang, said the train was not very far from the station when the victims were pushed.

"The man was very tall and strong," she said.

"I could get away but the lady couldn't, so he threw the ladies onto the tracks.

Ms Wang (left) said it was a dangerous situation when the man went on the attack. ( ABC News )

"I hid near the rubbish bin and then saw the man go into the station and catch another lady.

"He was calm. He didn't say any words."

Ms Wang described the incident as being "crazy" and said she did not want to go into the city anymore.

Sergeant Venturoni said police were still trying to work out a motive for the attack which happened very quickly.

He said it was all over in about 90 seconds.

"It's horrific for those involved. [They're] on the train platform, minding their own business and a male, for unknown reasons, has gotten off [the train] armed with a knife and attacked them," he said.

The man was arrested and was being questioned by police.