A man who died in a US prison where he was serving a sentence for rape also has been identified as a serial killer.

The Royal Canadian Mounted Police (RCMP) said Gary Allen Srery, who died in 2011 in an Idaho prison, strangled four girls or women in 1970s Alberta.

Srery may be responsible for more unsolved homicides and sexual assaults in western Canada, police said.

The victims were Eva Dvorak, 14, Patricia "Patsy" McQueen, 14, Melissa Rehorek, 20, and Barbara MacLean, 19.

All four lived in Calgary and disappeared between 1976 and 1977. Their deaths were investigated at the time as either suspicious or as homicides, but remained unsolved for almost half a century.

"For nearly 50 years, the Alberta RCMP exhausted all investigational means in an attempt to identify the person responsible for these tragic deaths," said Superintendent David Hall at a news conference on Friday.

A suspect was finally identified through advanced DNA technology, which allowed investigators to build a family tree using data from public DNA sites and samples found on the victims' bodies.

Eva and Patricia were in junior high in February 1976 when they disappeared while walking together in downtown Calgary. The following day, police said their bodies had been found on Highway 1 west of Calgary.

Ms Rehorek was a housekeeper who recently had moved to Calgary from Ontario for work. Police said her body was found in September 1976 in a ditch 22km (13.6 miles) west of Calgary, also a day after she vanished.

Police said Ms MacClean, who was working at a local food bank at the time of her death, had last been seen in February 1977 walking home after a night out at a bar with friends. Her body was found six hours later just outside Calgary city limits.

Superintendent Hall said that if Srery was still alive, he would be facing murder charges in the four deaths.

Srery was an American citizen who was in Canada illegally at the time of the murders, having fled the US after he was charged with rape in California, said police.

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