Dead whale believed to be "one of the largest" ever found in the Mediterranean.

The carcass of a huge fin whale found in the waters off Sorrento in southern Italy has been towed to the nearby sea port of Naples where marine biologists are now attempting to ascertain its cause of death.

The dead whale, which measures about 20 m long and reportedly weighs at least 70 tons, is "probably one of the largest" ever found in the Mediterranean, according to the Italian coastguard.

The carcass of the female whale was first spotted off Sorrento by coastguard divers last weekend, after a smaller, younger whale was filmed in the town's harbour in a clear state of distress.

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The disturbing footage, posted on YouTube, showed the young animal bashing its head against the harbour walls, leading to a significant loss of blood.

The disorientated mammal later disappeared into the sea and did not return to the harbour.

Experts suspect that the dead whale was its mother.

Photo: Antonino Maresca AMP, (Parco marino di Punta Campanella).