Police in Western Australia have made a breakthrough in a notorious 20-year-old "cold case" that has become one of the country's longest-running investigations.

A 48-year-old man was charged with two counts of murder on Friday in relation to the so-called "Claremont serial killings", which saw three women vanish from the wealthy Perth suburb of Claremont in Western Australia.

The remains of two of the women - Jane Rimmer and Ciara Glennon - were found in remote areas while the third, Sarah Spiers, remains missing.

For two decades police had been unable to solve the case, deploying hundreds of officers, offering cash rewards for information and taking DNA samples from 2,000 taxi drivers in Perth.

Over the course of the investigation, called "Operation Macro", police even recruited a convicted serial killer, David Birnie, to help crack the case.

Now police have charged Bradley Robert Edwards, who lives in the Perth suburb of Kewdale, about 12 miles east of Claremont, with the murder of Ms Rimmer and Ms Glennon, and with the sexual assault of two other women.

Police did not elaborate on what led them to Edwards.

Police say Edwards abducted Glennon, a 27-year-old lawyer, on March 14 1997, after she, too, had spent the evening out with her friends.

The investigation into the disappearance of Ms Spiers, an 18-year-old secretary, is continuing, Mr O'Callaghan said.

Edwards was also charged with abducting a 17-year-old in 1995 as she walked through a Claremont park.

The teenager was forced into a vehicle and driven to a cemetery, where she was sexually assaulted, Mr O'Callaghan said.

Edwards also faces an indecent assault charge after police say he broke into the bedroom of an 18-year-old woman while she slept and attacked her in 1988.

Edwards appeared briefly in Perth Magistrates' Court on Friday. He did not enter a plea and will return to court next month.