Loud explosions heard at Muriwai beach on Friday evening was the Defence Force detonating a "small cylindrical object".

Multiple residents heard loud noises about 9pm, not long after a water rescue took place at the surf beach, where a rescue helicopter was dispatched.

Police confirmed the incidents were unrelated and that a controlled detonation of an unidentified object took place.

A police spokesman said police were called in to help the Defence Force at 3pm after a "small cylindrical object" was found at Takapuna, on Auckland's North Shore.

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Police couldn't be specific about what the object was.

The object was taken to the bombing arena at Muriwai beach hours later, where it was detonated in a controlled explosion, the spokesman said.

The Defence Force has been contacted.