A woman has died and a man has been seriously injured following a shark attack on the NSW Mid North Coast early this morning.

Emergency crews were called to Crowdy Bay near the Kylies Beach campground around 6:30am after reports of two people being attacked.

Despite the efforts of bystanders, the woman,  believed to be in her 20s, could not be saved.

The man, also thought to be in his 20s, was treated at the scene and airlifted to John Hunter Hospital in critical condition.

The beach has been closed while authorities work to identify the species involved.

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