Mum describes man's alleged sex act at Sydney baby-friendly movie

A mother who witnessed a man allegedly masturbating during a mums and bubs movie session in Sydney's inner west says she feels "really sad and hopeless" her nine-month-old daughter has already been exposed to a sex crime.

NSW Police has appealed for information after the unknown man allegedly masturbated during a Bring Your Baby session inside Event Cinemas at Westfield Burwood about 11:20am on Friday.

The mum said she confronted the man, who attended the Social Reckoning session alone and was described by police as of Caucasian appearance, in his mid 20s and of medium build with short hair and a goatee.

The woman, who asked to remain anonymous while police try to locate the alleged offender, said the man was seated just one row in front of her and that she had initially leaned over to him to apologise in advance for her baby's fussing.

She said she later saw him moving strangely and realised he had his hands down his pants.

"It was undeniable what was happening, and I said, 'Excuse me, that is really inappropriate', and the other mum [attending the session] asked what was happening, and I said, 'He is touching himself'," the woman said.

"I said, 'You need to leave' … he said he wouldn't do it again, and I said, 'My baby is behind you, you need to leave'."

The woman said she then ran to the lobby for assistance and that the man eventually emerged from the theatre.

"He said 'I did it, but it wasn't about the children'," the woman said.

The man left the cinema before security arrived.

The woman said she and the sole other mother attending the Bring Your Baby session had tried to return to the cinema together to finish the film but decided to leave after five minutes.

She said she would not attend a baby-friendly session alone with her daughter again, and suggested cinema companies change their practices to help keep parents and infants safe.

"I already was hyper vigilant but now it's at a different level,"

she said.

"Having my nine-month-old daughter already exposed to a sex crime, there's so much going on in the world … I feel really sad and hopeless for my daughter and protecting her is my priority.

"Even having someone check your ticket at the door and do a risk assessment, then they could do a walk through [would help]."

An Event Cinemas spokesperson said the "Bring Your Baby" sessions had been providing a "safe and inclusive environment" for parents, caregivers and children for many years.

"Whilst this is an isolated incident, we are reviewing our practices for these sessions," the spokesperson said.

The man was seen Friday wearing a grey T-shirt, khaki cargo shorts, and carrying a dark grey backpack.

Anyone with information is urged to contact Burwood Police Area Command or Crime Stoppers on 1800 333 000.