Detectives are appealing for information after a woman was sexually assaulted and beaten by a stranger in west London.
Police were called shortly before 11pm on Thursday to Brouncker Road, Acton.
Officers searched the area with the assistance of the National Police Air Service, the Metropolitan Police said.
The victim, aged in her forties, is being supported by specially trained officers, police said, and enquiries are underway to trace the man responsible.
Detective Sergeant David Baldwin said: “At this time we believe the victim was attacked by a stranger and we are conducting extensive enquiries to track this man down.
“I am asking the public, if they have any information about this vicious attack, to come forward and tell us what they know. By sharing your information you can help keep our communities safer.”
Chief Superintendent Peter Gardner added: “This is a horrific and cowardly attack and my thoughts are with the victim who has gone through a terrifying ordeal.
“I appeal to you all, if you have seen or heard anything, please don’t hesitate to contact us.
“This is a dangerous individual and we will not rest until he is arrested.”
No arrests have been made, police said.
Anyone with information is asked to call 101 or tweet @MetCC and quote CAD8959/17SEP. To give information anonymously, contact Crimestoppers on 0800 555 111.