A 99-year-old woman has spent a week in hospital after a callous sexual assault in her own home, police say.
The great-grandmother was hit her over the head when she answered a knock on the door of her southeast Melbourne home.
She was then attacked for more than 30 minutes before she set off a panic alarm and the man ran off.
Police hope someone can identity the attacker from his distinctive dark T-shirt, which bears the words "Al fresco" across the front.
Detective Insp Glenn Davies said the attack had had a profound effect on the woman.
"She's had to remain in hospital for quite some time and for a woman of 99 to have suffered like this late in life, it's a terrible situation," he told reporters on Friday as officers released an image of their suspect.
The motive for the attack remains unknown.
"I don't know what the motive would be for someone to break in to a house where there was a woman who was 99 years of age and to physically and sexually assault her. I have no idea," he said.
The woman had been home alone at Ormond, in Melbourne's southeast, at around 10.30am (AEST) last Saturday when a young man knocked on her door.
He pushed the elderly lady back into the house to gain entry.
She suffered a head injury, cuts to her face and legs and remains in hospital, traumatised from the ordeal.
Police will set up an information caravan on Koornang Road, just north of Leila Road, between 9.30am-12.30pm on Saturday, in an appeal for public help.
The attacker is described as being of Caucasian appearance, aged between 17 and 20, approximately 160cm tall, with a thin build and brown straight messy hair.
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