The couple had been together for a year in Guidonia, north east of Rome, but in February she left him to return to work as a prostitute, Il Messaggero reported.
But the 74-year-old widow continued to stalk the woman, aged 56, who reported him twice to police.
On Saturday morning the pensioner, who was living off a disability pension, turned up by the petrol station where she would wait for clients and persuaded her to get into his vehicle.
He then drove her to a secluded spot where he reportedly stabbed her in the neck, arms and hands while she tried to defend herself. In the process she managed to grab the knife and throw it into the bushes before attempting to escape.
She ran 150 metres before one of the heels on her shoes broke causing her to fall. Her attacker then stabbed her in the abdomen and chest. Believing her to be dead, he then fled the scene.
She was discovered later by a passerby in a pool of blood and was taken to the San Giovanni Evangelista hospital in Tivoli.
In total the woman suffered five stab wounds and five broken ribs. Her wounds are not life-threatening.
The man has since confessed to the attack telling police “I attacked her because she hit me with a hammer”.
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He is currently under house arrest but is unlikely to go to jail because of his age.