Police are questioning a man over an attempted sex attack on an 81-year-old woman at her home in a retirement village, south of Perth.

The intruder broke into the Greenfields home about 2:00am on Sunday and grabbed the elderly woman, who was alone.

The man attempted to sexually assault the woman but she fought him off and the attacker fled.

Detective Sergeant Nicole Simon from said the woman received cuts and bruises to her face and swelling to her hand, and had been to hospital for treatment.

"We've spoken to her at length this morning," Sergeant Simon said.

"She's naturally shaken and upset by the incident but she is being cared for by family.

"It's a very cowardly attack, it's a vulnerable member of our community."

Police released a CCTV image of a suspect.

A man was apprehended a short time later.

Officers are calling for anyone with information, dashcam footage or CCTV from the Lakes Road area between Pinjarra Road and Waldron Boulevard in Greenfields to contact Crime Stoppers.