A cat killed a nine-month-old baby girl as she slept in her pram, police say.

Authorities were alerted after the girl's mother came into the back yard to check on her daughter after finishing housework.

She saw the family's cat lying on the baby's face. When the pet jumped off, she realised her daughter, Alexandra, was not breathing.

The backyard of the house and the bassinet where the baby was killed. Credit: East2west/Australscope

The Ukrainian mother, named as Snezhana, 22, called paramedics but they could not save the baby who died of asphyxia.

Halyna Zakharchuk, a medic who attended the scene said it appeared the cat had got inside the pram to warm up.

"When we came, the baby was still warm," she said. "We could not help…we were trying to resuscitate her for 30 to 40 minutes.”

Local police confirmed the cat was sleeping on the baby's head.

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"The body was sent to forensic experts, an autopsy was performed," an officer said, confirming the death was being treated as accidental.

"The preliminary opinion of the expert is that it was asphyxia. There are no more injuries on the baby’s body.”

The baby was Snezhana’s only child with her husband Alexander.