Andrew Cunningham went missing from an address in Blackburn on Saturday, breaching his licence conditions.
The 35-year-old was convicted of three sex assaults in Manchester in 2007, 2011 and 2016.
Cunningham has links to Morecambe, Lancaster and Blackpool and was seen on CCTV at a shop in the Chadderton area of Greater Manchester yesterday.
Anyone with information about his whereabouts is urged to contact police immediately.
Det Sgt Steve Munro, of Lancashire Police, said: “Cunningham has been wanted for several days now and is in breach of his licence requirements.
“He has strong links to the Manchester area and we believe he is likely to be somewhere in the city.
“Cunningham is a prolific and dangerous offender. I would advise anyone with information not to approach him but to contact police immediately.”
Anyone with information can contact police on 101 quoting log reference 1237 of November 24.
Alternatively, independent charity Crimestoppers can be contacted on 0800 555 111 or online at crimestoppers-uk.org