A 21-year-old man has been arrested on suspicion of murdering a man and sexually assaulting a woman.
Police were called to a house in Turin Court, Andover, Hampshire, at 3.11am on Monday following a report of a serious assault.
A 26-year-old man was pronounced dead at the scene by paramedics.
A Hampshire Police spokesman said that at 3.55am, a young woman reported that she had been sexually assaulted at a house in Little London, near Andover.
He said: "A 21-year-old man from the Andover area has been arrested in connection with both incidents and is currently in police custody."
Detective Inspector John McGonigle said: "Our inquiries are ongoing but we would really like to hear from anyone who has information about what happened.
"Were you in either the Turin Court area of Andover, or in Little London, that night? Did you hear or see anything that you think could help our investigation?
"Perhaps you noticed something suspicious that night and have not reported it to police yet.
"If so, please call us on 101, quoting Operation Goldcrest."
Chief Inspector Kory Thorne, district commander for Andover and Test Valley, said: "We know this will be concerning to residents but I would like to reassure them that detectives are working hard to determine what happened.
"Officers will carry out house-to-house inquiries in the coming days, so residents will see additional police officers in the area.
"Our neighbourhood officers are patrolling the area, so if you have any concerns, please don't hesitate to approach them."