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The woman was returning to her Thomson St home shortly after 1am when she was confronted at her front door by a male intruder who grabbed her by the throat, Senior Sergeant Steve Aitken said.
"She defended herself by kneeing him in the groin," he said.
The man, who was wearing dark clothes and a balaclava, ran off.
Police patrols in the area failed to locate the man.
Snr Sgt Aitken praised the actions of the woman, who was left shaken from the incident.
"She did a fantastic job in protecting herself," Snr Sgt Aitken said.
Police believe the man, who was between 170cm and 180cm tall and of medium build, had been trying to gain access to her property at the time she returned home.
Snr Sgt Aitken said police were also investigating another reported case of a balaclava-clad man in dark clothing at Green Island School on Friday night.
He reportedly accosted two youths.