We've heard of raining cats and dogs and plagues of frogs falling from the sky in ancient Egypt but Melbourne motorists were dumfounded when 400 sheep crashed on to a busy freeway.

A lorry, carrying hundreds of sheep, crashed on a flyover, leaving the rear of the vehicle hanging precariously over the parapet. The livestock lorry's cargo slipped to the back of the vehicle and its combined weight pushed open the truck's doors, depositing livestock all over the road below.

Terrified drivers had to veer and brake wildly as the terrified animals crashed to the ground. A number of cars were wrecked.

Hundreds of sheep were killed or injured but police say there were no human casualties.

Police said the truck was travelling to the town of Geelong. It crashed on a flyover above the Princess Freeway in Melbourne.

"We looked up and we could see the truck flip on its side and then the next minute, we were underneath and yeah, raining sheep doesn't happen everyday," said road-user Kristy Davis.

"This is quite an unusual event," Allan Eade, a paramedic, told the Associated Press.

"They were confronted with a very horrific, very distressing sight," the Royal Society for the Prevention of Cruelty to Animals said.

Egypt