Police are urging Newcastle parents to walk their children to school after an 11-year-old girl was abducted and sexually assaulted during a five-hour ordeal.

The girl was walking through Hudson Park in the suburb of Adamstown Heights on her way to school just after 9.15am yesterday, when she was threatened with a knife by a man who sexually assaulted her, police said.

She was then forced into a red car, believed to be a Commodore sedan, and driven to bushland where she was sexually assaulted for several hours before being released at Kotara Railway Station just before 2.15pm - about 1.5 kilometres from where she was abducted.

Police tape off around a primary school to investigate the sexual assault incident. Picture: 9NEWS (9news)

Det Chief Insp Jacob speaks to the media. Picture: 9NEWS (9news)

Police were called when she returned home and the girl was taken to John Hunter Hospital for medical examination.

"An 11-year-old girl was approached from behind by a male offender and attacked, threatened with a knife, sexually assaulted, placed in a car and driven to another location in bushland where she was further offended again," Child Abuse and Sex Crime Squad Detective Chief Inspector Paul Jacob said.

"She reported it to her grandmother. She's now in the safe custody of her parents.

"We're looking for a male offender. We cannot be specific on his age but he is described as being chubby with dark, short, messy hair. He has wrinkles on his forehead and around his mouth. He has brown staining on his teeth. He has chubby hands.

"I should say that he had a distinctive-coloured hoodie on. It was a dark grey and black hoodie with a blue colouring at the waist-level at the bottom of the front. He had it zipped up over his chin and mouth. That prevented the young lady from seeing his full description."

A police photographer investigates the Newcastle incident. Picture: 9NEWS (9news)

The area has been cornered off as police investigate. Picture: 9NEWS (9news)

Det. Chief Insp. Jacob said it was "quite a worrying crime committed in broad daylight to a very brave young girl".

"It's our mission to get this person and remove him from the community as quickly as we possibly can," he said.

"I don't want to limit people to that time-frame yesterday. I want them to look to the days before. I want people who were driving in that area to consider their dashcams."

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Det. Chief Insp. Jacob said the 11-year-old was doing "remarkably well".

"She's a very brave, young lady who has intensely assisted the police in a remarkable way throughout the evening and into the late evening," he said.

"She walked home, it's about 1.5 kilometres, from where she was dropped off at the railway station.

"I cannot forecast what could have happened but any attack on a young girl and a woman is horrible and these were a horrible series of attacks on the young lady."

Police have been combing through bushland at Adamstown Heights after the girl, aged 11, was abducted and sexually assaulted. Picture: 9NEWS (Nine)

Police have been searching through the bushland where the girl was attacked over five hours. Picture: 9NEWS (Nine)

Resident Lee Graham told 9NEWS the incident was "horrifying".

"I only live around the corner. I can see where they've (police) taped off from my house. I feeling pretty concerned at the moment," Mr Graham said.

"I've got two girls in school so it's pretty concerning.

"The police asked to speak to us because we live so close. They pretty much said maybe not let the kids walk to school on their own at the moment.

"We've got the high school just down the road so kids walk around, kids play in the bush, kids play in the park. We try to encourage that. We try to encourage kids to go out to play on their own.

"I really hope they catch the guy soon."

A crime scene was established at Hudson Park and forensically examined while Newcastle police and the Child Abuse and Sex Crimes Squad have commenced inquiries.