Police said the 19-year-old was approached by two men in Buckland as she walked along Lake Road between midnight and 1am this morning, who continued to follow her to Turner Road, where the incident then took place.
An area near and around Ark Dickens Primary School was taped off and evidence markers laid out on the ground as officers carried out enquiries today.
Three 18-year-old men, a 17-year-old boy and 16-year-old boy, all from Portsmouth, have each been arrested on suspicion of rape.
A police spokesman said: ‘They remain in custody at this time.
‘We remain keen to speak with anyone who may have information which could assist our enquiries.
‘If you saw anyone acting suspiciously around the area of Lake Road and Turner Road last night, or if you have dash cam or CCTV footage from the area, then please contact us.
‘You will continue to see officers in the area this evening.
‘If you have any concerns or information, please do not hestitate to speak with them.
Anyone with information can also call 101, quoting the reference 44200364429. Alternatively, you can call Crimestoppers anonymously on 0800 555 111.’
The woman is currently receiving support from specialist officers.
Detective Inspector Emma Crute said: ‘This has been a very distressing incident for the victim and I want to urge anyone who may be able to assist our enquiries to get in contact with us as soon as possible.
‘We believe the men may have been disturbed by a car driving close by. We urgently want to speak with anyone who may have driven along Turner Road just before 1am this morning.’