Two venomous snakes have been captured on camera as the pair were locked in a fierce fight in Adelaide's south.

Walkers were enjoying the warm weather in Onkaparinga River Recreation Park when they spotted a brown snake and a red-bellied black snake fighting on the weekend.

The pair were wrestling just two metres off the walking trail.

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The woman who recorded the video said "the brown snake had the whole head of the red-bellied black snake in its mouth and was squeezing and pulsing".

"Look how many times the brown is wrapped around it," the woman said in the video.

"One, two, three – I reckon it's wrapped around like six times.

"Oh, mate."

It is not clear which snake ended up winning the fight.