A 21-year-old woman woman was allegedly sexually molested by a stranger in St Mary's churchyard early on Sunday.
The victim was allegedly attacked by an Asian man in his 30s on the grounds of St Mary's Church in Aylesbury town centre in the UK.
Thames Valley Police said the alleged attack took place between 5.30am and 6.15am, with the woman able to call the force at around 6.40am.
Senior investigating officer Detective Inspector Jason Simpson of Force CID, based at Milton Keynes police station, said: 'The incident reported is naturally very concerning and the victim is being supported by specially trained officers at this time.
'We are in the very early stages of this investigation, and are conducting thorough enquiries to ascertain exactly what has happened.
'I am appealing to anybody who was in the general vicinity of St Mary's Church or adjacent streets in the early hours of this morning to please contact Thames Valley Police if you believe you witnessed anything that can assist this investigation.
'I would also like to hear from anybody in the local area who may have been driving and has dash-cam, to please check this and contact us if it has captured anything.
'I would like to reassure the local community that we are investigating this as a priority, and there will be a considerable and very visible police presence in the area while these investigations continue.
'We currently have a scene-watch in place in St Mary's Churchyard, and expect this to remain in place for some time.
'Our investigation also includes house to house and CCTV enquiries, and so if anybody living nearby has CCTV installed, please check this and get in touch if it has captured anything that can assist us.'