Two boys under the age of 16 have been arrested on suspicion of sexually assaulting a woman.
Police said members of the public reported the attack at around 9.30pm last night in Epsom, Surrey.
The two schoolboys were detained by witnesses before being arrested when officers arrived.
The lead detective in the case has praised onlookers for their quick thinking.
In a statement, Surrey Police said the attack happened close to Ye Olde Kings Head pub.
Detective Inspector Andy Skoglund said “We would firstly like to thank the quick thinking, observant members of the public who assisted in helping the victim and have been helping us with our initial enquiries.
“We have spoken to many witnesses already who were predominately outside the Ye Olde Kings Head Pub on Church Street but looking to anyone who may have any more information to get in contact with us.
“If you have any dashcam or CCTV footage of Church Street, Rosebery Park, Heathcote Road, Downside or St Martin’s Avenue taken around that time you may be able to really help us with this investigation.
“Local residents will see us on scene for the remainder of the day whilst we carry out our enquiries and may notice an increased police presence over the next couple of days.
"This is nothing to be concerned out and we ask that you please respect the cordons that are in place.”