One of the world's rarest birds - once thought extinct for over 300 years - has been spotted off the Kerry coast.

The Bermuda petrel, better known as the Cahow, was observed by crew members of the Celtic Voyager - the Irish Marine Institute's research vessel.

The "astonishing" sighting of the endangered seabird took place off Kerry on Monday. Within hours, the Bermuda Audubon Society confirmed the report through data emitted by the bird's electronic geolocator.

The medium-sized Cahow is the national bird of Bermuda.

It is currently being "laboriously brought back from the brink" by conservationists with only about 180 of the species known to exist.

A slow-breeding ground-nester, the bird was wiped out during the 1600s when colonisation of the North Atlantic island introduced species such as boars, cats, dogs and rats.

It was rediscovered on the island in 1951.

The RV Celtic Voyager crew including Niall Keogh and Ryan Wilson-Parr, spotted the bird as they undertook a survey of cetaceans and seabirds about 170 nautical miles north west of Slea Head.

They filed a report with the Irish Birding website which noted: "It was on view for a maximum of one minute before heading off in a south east direction."

BirdWatch Ireland development officer Niall Hatch described the sighting as "astonishing". He said it was the first official sighting of the bird in Irish waters.

"This is a species that had been thought extinct for over 300 years until its dramatic rediscovery in 1951 and, since then, it has been the subject of a remarkably successful conservation project," said Mr Hatch.