The three women were assaulted in Cassiobury Park on Monday 8 November at around 12pm.
Officers are appealing for witnesses and information after it was reported that an unknown man approached one woman, shouting at her before kicking her in the stomach and grabbing her.
Two other women came to help, but they then were also assaulted and the man spat at them.
The man then ran off fleeing the scene along the Grand Union Canal alongside the park, in the direction of the Grove.
PC Jonny Lister, who is investigating, said: “This was a completely unprovoked attack, which has understandably left the victims shaken up. The suspect was described as a white male who was around 5ft 7in tall, with dark hair and stubble. He was said to be wearing dark clothing, and had a grey sweatshirt tied around his waist.
“I would like to appeal to anyone who was in the park around the time specified, who believes they may have witnessed the incident or seen a man matching the description behaving suspiciously, to please get in touch. It was reported that several people intervened, and we would like to speak to them as soon as possible.
“Any information, even something that may seem minor or insignificant, could be key to progressing our investigation.”
Anyone with information can contact PC Lister directly via email at email@example.com quoting crime reference 41/87493/21.
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