Two women have been targeted in a rape and attempted rape in the Beverley Road area.
The two attacks occurred in roads off the busy street between Thursday and Saturday, with one target able to escape thanks to a quick-thinking member of the public.
In another incident, a woman was raped near a narrow cycle track close to Cave Street.
Police say they do not believe the incidents are linked.
The first attack involved two bare-chested men who reportedly attempted to rape the victim by pushing her to the ground in broad daylight on Thursday lunchtime.
It happened at around 11.30am on Thursday, near Station Drive. The men were described as between 27 and 37 years old.
One was said to be wearing a denim jacket without a t-shirt beneath it and the other was said to be topless.
The attack was spotted by a member of the public who raised the alarm, forcing the men to flee the scene.
The second incident happened as a woman who was walking along a cycle track was approached by a man.
He is understood to have spoken to her before the attack began.
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He is described as around 35 years old, shorter than 5ft 5in and had dark, spiky hair.
Both women are being supported by specially trained officers from Humberside Police and the force say they are "treating both incidents as a priority".
High-visibility patrols have begun in the area and people are being urged to use well-lit routes and stay with family members or friends when walking the streets.
Detective Inspector April Cook said: “I want to be really clear that we do not believe these incidents to be connected, however we are asking people to please be aware and to take steps to protect themselves when they are out and about.
“When out walking, remain with a trusted friend or family member where possible and try to use well-lit busy roads for your journey.
“If you believe you have witnessed any suspicious behaviour please do call to get in touch with us.
"We are treating both incidents as a priority and have already carried out various investigations, including reviewing CCTV in the area.
“Specially trained officers are offering their support to both women and we have high visibility police patrols in the local area to provide reassurance.
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"We are appealing for witnesses to either incident and are particularly keen to hear from the man who shouted at the men in the first one near to Station Drive, or anyone in the area for either incident.
"If this was you or you have any information, please call our non-emergency 101 line quoting log 240 of 21 May or log 35 of 23 May.”
Alternatively anyone can report information anonymously via Crimestoppers on 0800 555111.