A 46-year-old man has been arrested on suspicion of raping a woman in a churchyard.
Thames Valley Police (TVP) reported the 20-year-old victim had been attacked by a man in the grounds of St Clements Church in Marston Road, Oxford.
The incident occurred between 03:00 and 03:30 GMT on Sunday while she was walking back from the city centre.
Det Sgt Lisa Jones appealed to a man and a woman who had intervened in the incident to contact the force.
TVP is also urging people who left the Half Moon pub and may have seen or spoken to a man and a woman outside Taylor's Estate Agents to come forward.
Drivers with dashcam footage and any witnesses who were in the St Clements Street area, or near the church, have been told to get in touch.
Det Sgt Jones, of Oxford CID, said they were investigating the incident "as a priority".
She extended the appeal to "anybody who believes that they witnessed this incident or any suspicious activity" in the area of Marston Road.
She added that even though it caused "a great deal of concern" she reassured the local community that they believed it to have been "an isolated incident".
The suspect remains in police custody and the woman is being supported by specially trained officers.