The beluga whale who strayed into the River Seine in France has died following a massive rescue operation involving 80 people.

The all-white beluga had swum nearly halfway to Paris before local authorities confined it in a large lock system.

"Despite an unprecedented rescue operation for the beluga, we are sad to announce the death of the cetacean," the prefect of the Calvados department, said on Twitter.

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Hopes had been raised on Wednesday morning with the extraction of the 800 kg (1,760 lb) cetacean which took over six hours. 

It was being transported in a refrigerated lorry to the coastal town of Ouistreham, in Normandy, before being put in a salt water lock.

The first stage of the rescue operation was a success but there remained huge concerns over the survival for the whale, which should normally weigh 1,200 kg.

Isabelle Dorliat-Pouzet, secretary general of the Eure prefecture, had earlier said: "It's horribly thin for a beluga and that does not bode well for its life expectancy for the medium term."

In late May, a gravely ill orca swam dozens of miles up the Seine and died of natural causes after attempts to guide it back to sea failed.

In September 2018, a beluga whale was spotted in the River Thames near Gravesend, east of London, for a few days, in what was then the most southerly sighting of a beluga on British shores. The whales typically live in pods in Arctic coastal waters.