Flying sheep cause pile-up in Melbourne, Australia (VIDEO)

Hundreds of sheep were sent flying onto a freeway in southern Australia today when a livestock truck overturned.

The truck was carrying 400 of the animals when it flipped onto its side on a bridge above the Princess Freeway outside Melbourne, The Age reported.

Dead and injured sheep plummeted onto the highway below, some hitting vehicles directly and others piling up on the road.

Several cars crashed. Police told the Associated Press that one vehicle rolled over four times, while three were written off when sheep fell through their windscreens.

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One witness said it had been "raining sheep."

"There was nothing we could do, they were literally on top of us," driver Hannah Sidebottom told the AP. "We just ran straight through them, we all screamed. […] My car is an absolute write-off, but the sheep – I just feel so bad for them."

No humans were seriously injured, according to the BBC, but there were heavy casualties among the animals.

According to animal protection officers, fewer than 10 of the sheep survived. Some were killed instantly while at least 50 had to be put down, RSPCA Victoria spokeswoman Kristen Vear told Nine MSN News, describing it as the worst animal accident her colleagues had ever seen.

A cattle truck overturned on the same freeway last month, The Age said, with the police air wing called in to round up the scattered cows.