Local officials in Piraeus, near the Greek capital, said they have also launched a public awareness campaign to prevent the fish from being caught or consumed.

Otherwise known as Lagocephalus scleratus, the fish carries dangerous toxins in its entrails and skin which can be lethal to humans. Covered with dark spots, it has two silver lines on its flanks and a beak-shaped mouth with four large teeth.

Three puffer fish were caught Sunday off the island of Salamine, local authorities said in a statement.

"Increased vigilance is advised" as the fish can be easily confused with a sardine or whitebait, it said.

The fish were first spotted in Greek waters in June 2007 around the islands of Rhodes, Symi and Crete in the southeastern Aegean, but this is the first time they have been found near Athens.

Greek scientists say warmer waters have caused the fish to migrate further north in the Mediterranean.

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