THE two girls sexually assaulted by a man in a public toilet in a western Sydney park while their parents were having a picnic less than 100m away are undergoing counselling at Westmead Hospital.

NSW police have made a public appeal for people with any information to come forward.

As the investigation enters a second day, Detective Peter Yeomans said the force is throwing all the resources it has into finding the man who followed the two girls into the public toilets at Campbell Hill Pioneer Reserve at around 1:30pm yesterday.

He is described as being of Middle Eastern or Mediterranean appearance, 165cm tall, with dark hair, a chubby build, and aged in his 30s.

The park has been closed to the public since the assault on the six-year-old and her younger sister who were just 30m from where their family was enjoying lunch.

"It is a very harrowing situation for the family. They are very, very deeply stressed by what has occurred to them and to their children," Detective Yeomans said in a press conference this morning.

"Both children were already in the toilet (before the assault took place).

"The little six-year-old was taking the two-year-old to the bathroom and was assisting the two-year-old.

"The adult male then entered that bathroom area and assaulted the children."

The girls were taken to hospital­ after the attack but the extent of their injuries is unknown.

Asked about their condition, Detective Yeomans added: "The little 6-year-old is still very upset by what has occurred.

"The little 2-year-old when it did occur was very upset, was crying but they are receiving counselling through various counselling services at the Westmead children's hospital.

"There were a number of people at that park at the time who may or may not have seen something and anything that they did see or they may have filmed something, we are asking them to come forward and contact their local area command or Crime Stoppers."

Detectives from the child abuse squad have formed Strike force Sandyman to further investigations after police officers, the dog unit and Polair failed to find the man yesterday.

News_Image_File: Police investigators at the scene / Picture: Peter Kelly

Police are currently looking into whether any CCTV footage from business and residential areas will aid with the investigation.

Detective Acting Superintendent Peter Yeomans described the attacks as ``a parent's worst nightmare''.

``The parents involved in this are absolutely devastated and so is the immediate family,'' he told Macquarie Radio today.

``It's horrific, what has happened to them.''

A large group of angry residents­ gathered outside the popular park, which has a family­-friendly shaded playground and several covered eating areas, after the attack.

News_Module: Campbell Hill Reserve Guildford

A resident identified only as Maysa said that she knew the family: "It's shocking. I don't know what to say. It's disgusting. There's no words to describe how I feel, especially how the family feels.

"They must be devastated. You don't know what to say. It's disgusting, he should be burnt, dead. No little kid, no family deserves this.''

News_Image_File: Local residents gathered at the scene and expressed their disgust and disbelief / Picture: Peter Kelly

Marina Smith-Thorne from Chester Hill told police at the scene she had seen a man of a similar description leaving the women's toilets in October but, until now, had not thought anything of it.

"I wish I'd said something at the time. I was walking into the women's toilet with my two little­ boys when I saw him walking out and I thought 'What's he doing in the women's toilet?' she said.

"He just sheepishly walked out. At the time I didn't think anything of it.

"I just heard the description on the news and said to my husband, 'That sounds exactly like the man I saw'.''

Several families stayed in the park hours after the attack, with one woman saying she saw a man run from the toilet block.

Police, the dog squad and a police helicopter searched the park and the surrounding area. Police sealed off the park entrance­ as forensic officers and detectives examined the women's toilets, just 10m from the road.

News_Image_File: The toilet block where the girls were assaulted / Picture: Peter Kelly