A suspected rapist wanted over the abduction of two women off the streets of London allegedly attacked another woman days before.
Joseph McCann is suspected of snatching a 21-year-old woman at knifepoint in Watford in the early hours of April 21 and raping her, Hertfordshire Police said.
It has since emerged that McCann is being hunted by the Metropolitan Police over attacks on two women in their 20s in north London on Thursday.
The force is offering a reward of up to £20,000 for information which leads to his arrest and prosecution.
The Met Police warned that he is "extremely dangerous" and known to use false names and may be using a disguise.
Officers in Hertfordshire investigating the earlier sex attack circulated the name of the fugitive in a public appeal last week and said the 34-year-old was wanted on recall to prison.
It is understood he had been released on licence from prison in February 2017 for an aggravated burglary.
Hertfordshire Police said the first woman was approached at around 3.30am on April 21 in Hagden Lane, driven around for six hours in a blue Ford Mondeo and then raped.
The ordeal was reported to police the following day.
A spokesperson said: "The matter is being linked to the offences currently being investigated by the Metropolitan Police Service.
"We have been working very closely with them since their offences were reported and work is ongoing to trace the suspect."
Police described McCann as being muscular, about 5ft 10in, and having a "distinctive" tattoo of the name "bobbie" on his stomach.
He is said to have blue eyes, a bald head or shaved blond hair with a light-coloured beard, and a "slight" Irish accent.
Officers said he has recently gone by the name of Joel and has links to Watford, north-west London, Aylesbury, Buckinghamshire, and Ipswich in Suffolk.
Both women were raped after being snatched by a man in a silver or grey-coloured Ford S-Max people carrier with false registration plates.
The first woman was abducted at about 12.30am on Thursday from a street in Chingford, before the second was seized around 12 hours later at 12.15pm from a street in Edgware.
One of the women may have been pregnant, The Times reported.
They were driven to a hotel where the man attempted to book a room at around 1pm.
They left when this was unavailable.
But the women managed to escape in Osborne Road, Watford, at about 2.30pm.
They were both "traumatised" by the ordeal and are receiving support from specialist officers, police said.
Detective Chief Inspector Katherine Goodwin said: "We would ask anyone with any information about McCann's whereabouts to contact us immediately - McCann is considered extremely dangerous and a risk to the public and we ask people not to approach him, but instead call 999.
"If you wish to remain anonymous, call Crimestoppers. It is vitally important we trace him in connection with these offences."
A 33-year-old man has been arrested on suspicion of conspiracy to rape, while the hunt for the rapist continues.
Crimestoppers can be contacted anonymously on 0800 555 111.