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A pregnant shark at a New Zealand aquarium was bitten by another shark, unexpectedly releasing four baby sharks as visitors watched.

An aquarium spokeswoman said stunned visitors saw the injured shark and alerted staff that they had also seen things float from the gaping wound.

The baby sharks were removed from the tank to prevent stingrays and other sharks from eating them.

When staff also moved the mother they found a further four sharks inside her.

The mother's wound was stitched by a vet at Kelly Tarlton's Underwater World in Auckland.

"She's doing well, but we're watching her closely as it's a one-off occurrence, so we're not sure how she'll do," a spokeswoman told the BBC.

All eight baby sharks survived.

Aquarist Fiona Davies, quoted by the NZ Herald website, said it was common for sharks to take chunks out of each other, even in the wild, but she had never heard of anything like this.

Ms Davies said the unusual delivery had probably saved the baby sharks' lives.

If the mother had given birth naturally, most likely at night, the babies would have been eaten by adult sharks and stingrays before staff could rescue them.