A woman aged in her mid 30s is being given specialist support after an incident in Yeovil.
She was sexually assaulted in the West Hendford area at around 3am on Sunday morning.
The victim was pulled to the ground and detectives say the offender ran off after she fought back.
Detective Sergeant Mark Probert said: "We know this incident will be of concern in the local community and I'd like to reassure the public that a full investigation is already under way.
"The victim will be given any help or support she may need.
"We want to speak to anyone who was in the West Hendford area of Yeovil around the time of the incident, particularly if they saw or heard anything suspicious.
"We'd also like people to call us if they recognise the description given or have any other information which could help?
"The offender is described as white, mid-thirties, about 5ft 5ins, of stocky build, with short dark hair and spoke with a foreign accent. He was wearing a hooded top."
"If you can help, please call Investigations on 101 and give the call handler the reference number 5219046383."