Ryan Humpage, who is described as dangerous, is wanted by police in Lancashire after he was charged with the rape of a 13-year-old girl.
Police said he breached his bail conditions.
Mr Humpage is understood to have friends in Belfast.
Police in the Republic of Ireland say there have been reported sightings of him in counties Sligo and Kildare.
They say he may be using various other names, including Dylan Dunne, Ryan Willington, Ryan Williams and Karl Ward.
Mr Humpage's case has appeared on the BBC's Crimewatch programme.
Police on both sides of the Irish border are searching for an 18-year-old man who is wanted in the UK over rape, theft and assault allegations.