A Japanese city has been put on alert after five packages of potentially poisonous fugu (pufferfish) meat were mistakenly sold by a local supermarket.

Fugu is considered a delicacy in Japan, but requires careful preparation to remove toxic parts of the fish - such as the skin and liver.

AFP news agency reports that five packages of the fish without the liver removed were sold in the city of Gamagori in central Japan.

It prompted an emergency response from local authorities, with loudspeakers across the city being used to urge residents not to eat the fish.

While three of the five packages sold have been found, two others have yet to be recovered.

Local official Koji Takayanagi told AFP: "We are calling for residents to avoid eating fugu, using Gamagori city's emergency wireless system.

"Three packages will be retrieved today, but we still don't know where the remaining two are."

The Asahi Shimbun newspaper reports that the supermarket in question has apologised for the error, insisting it will not sell the fish again.

Certain parts of pufferfish contain tetrodotoxin. If consumed, it can lead to paralysis and even death in extreme cases.

Pufferfish liver is banned from sale in Japan.

Chefs in Japan require years of training and a special licence before being allowed to prepare the delicacy, which is typically served as either sashimi (raw fish) or in a hot pot.

Data from Japan shows several deaths most years as a result of fugu poisoning, with dozens of other diners treated for non-fatal symptoms.