A man suspected of killing two people in their own homes is a known drug user who had been released on court bail, the detective leading the manhunt has said.
James Allen has previous convictions for violence and has served a custodial sentence, Detective Chief Superintendent Gordon Lang told a press conference in Middlesbrough.
The 35-year-old suspect is being urgently sought by police following the separate murders of Julie Davison, 50, in Whitby, North Yorkshire, and 81-year-old Colin Dunford in Middlesbrough.
The detective said there had been a number of reported sightings of Allen in Middlesbrough, Scarborough and Whitby as detectives stepped up the manhunt.
He urged the suspect to give himself up, saying: "James Allen, stop now. Do the right thing. Consider the consequences. You have inflicted terrible injuries and death on two families. Stop and hand yourself in."
Mr Lang confirmed Allen was on court bail for an offence, although he did not disclose what it was. He also said that Allen had had contact with the probation services and was being investigated for other alleged offences, which he would also not disclose.
Mr Lang said: "People should take common-sense precautions, safety first. Lock their doors, lock their windows and check who's knocking on your door. Clearly this is a man who is a dangerous man, but we are putting absolutely everything into finding him, tracking him down and bringing him to justice."
Mr Lang said Allen, originally from Blackpool, knew Mr Dunford when he lived next door to him in Leven Street about a year ago. The officer said it was not thought Allen knew Ms Davison.
Cleveland Police and North Yorkshire Police issued a joint appeal to find Allen after officers linked the two deaths on Thursday. A post-mortem examination on Mr Dunford, who was last seen alive at around 5pm on Sunday, showed he had suffered serious head injuries as a result of a significant assault. Ms Davison, who lived alone, was found dead by her sister at her rented flat in Church Square on Wednesday. She had also suffered serious head injuries, police said.
Cleveland Police later said that sightings of Allen were continuing to be reported in both police force areas. Mr Lang said he believed Allen to be involved in "a number of other offences" and urged people to take precautions in their homes to stop him from committing any further crimes. Anyone with information about the murders is asked to contact the non-emergency number 101 and ask for Cleveland Police.