THE parents of murdered twins Claire and Diane Sanderson last night appealed for help in catching the killer.

They made their appeal as it was revealed that the double killing was being linked to the deaths of frail pensioners Joan and James Britton hours later.

And police renewed their warnings for the public not to approach 34-year-old Mark Richard Hobson, the man they want to speak to "as a matter of urgency" in relation to the murders.

Claire and Diane, 27, were found dead at a house in Camblesforth, Selby, North Yorkshire, at about 8am on Sunday, where Claire had lived with Hobson for the past three months.

Diane had been strangled and had also suffered a number of other injuries. Her sister had also been subjected to a violent assault although her cause of death has yet to be established.

Shortly before 11.30am the same day, police were called to the Brittons' £400,000 detached home in Strensall, York, by a neighbour. Their bodies were found downstairs. Mr Britton, 80, and his 82-year-old wife had both been stabbed and beaten.

The couple had two daughters, one who lives in Durham and the other in South Africa.

Detective Superintendent Javad Ali, who is leading a 100-strong team of officers, said: "We have a confirmed sighting of Mark Hobson, in Wiggington Road, York, at about 2am on Sunday.

"We have now established possible sightings of a man whose description is similar to that of Mark Hobson in the Strensall area at 9.15am that Sunday.

"This , with other evidence recovered from both scenes, indicates that the two incidents may well be linked."

He said there had also been some similarities between the injuries.

The bodies of the Sanderson twins were found by their father, George, and Diane's boyfriend.

From their home in East Cowick, near Selby - where Diane also lived - Mr Sanderson and his wife, Jacqueline, said: "Words cannot express how we feel about the sudden and unexplained deaths of our two beautiful daughters.

"We would urge anyone who has any information which could assist the police to contact them."

Mark Hobson, a former binman with a record for grevious bodily harm and theft, is a divorced father-of-three. Anyone who sees him is urged to call police on (01904) 669651 or Crimestoppers on 0800 555 111