The Daily Telegraph can reveal police in the Hills Local Area Command are pursuing seven men associated with the gang over their menacing standover attempts on young teens.
The investigation, codenamed Strike Force Jounama, has been running since late last year and is probing up to 15 separate cases of violence and standover.
One saw the parents of a boy pay thousands of dollars to stop a group of men targeting their son and threatening to harm him.
Inspector Gary Bailey said children from the age of 16 were being targeted and more witnesses were being sought.
He said their main person of interest was a man aged 23-25 who was seen in full Hells Angels colours at several major shopping centres.
"He was common to shopping areas around the Hills and they've taken action to get rid of him," Insp Bailey said.
"We're seeking at least half a dozen others linked to the gang - these people were standing over people and committing acts of violence."
Police have been told the man and others were using several major shopping centres as recruitment grounds.
The Gangs Squad and Strike Force Raptor has also been brought in to assist with the investigation.
A number of people told police they were the victims of robberies.
It then took some time before links to the Hells Angels were established.
Insp Bailey said several witnesses had provided statements about the intimidation.
Others were reluctant.
"It is a priority for police to protect the anonymity of anyone who supplies us with information," he said. Inquiries have revealed the deliberate targeting of youths is not just confined to the Hills district. "We know it's going on in other areas," a senior police source said.
Officers released a CCTV image of their main target taken at one of the shopping centres following enquiries made by local newspaper the Hills Shire Times.
Police have previously voiced serious concerns over bikie recruitment of teenagers, particularly the Hells Angels, who are known to use youngsters to commit crime.
Baulkham Hills MP David Elliot said last night it was an extremely concerning matter. "If anyone feels anxious about this matter they can come into my office and we'll walk them down to the police ourselves," he said.
"We're calling any witnesses to give information to the police and if they feel threatened about it, they need to rest assured the police and certainly the community leaders will be right behind them."
In April last year two 17-year-old alleged associates of the gang were arrested over two drive-by shootings in Merrylands, which were targeting rival gang the Nomads.
Opposition Leader John Robertson has called for the O'Farrell Government to "ban the bikies".
"The Hells Angels should be banned and banned today," Mr Robertson said. "The Premier has the power to declare these bikie gangs outlawed … why isn't he using it?
Mr Robertson said the gangs were "running riot" in the suburbs, "terrorising young people, shooting up homes and threatening families".
"Barry O'Farrell needs to stop sitting on his hands," he said. "Police have wanted to declare the Hells Angels bikie gang a criminal organisation since April last year, why hasn't it happened?"
The O'Farrell Government reinstated anti-bikie laws in March 2012 but they have never been used.