Image copyright AFP Image caption Fugu - the Russian roulette of dining?

A Japanese city has broadcast emergency warnings to prevent people consuming blowfish, after potentially deadly portions were mistakenly sold.

A local supermarket in Gamagori city sold five packets of fugu fish without removing the livers, which contain poison.

Three have been found but two remain missing.

The delicacy is so poisonous that the smallest mistake in its preparation can be fatal.

Each year there are several cases of fugu poisoning in the country, but not all are lethal.

City authorities in Gamagori, in central Japan, have activated an emergency system, urging people to return the potentially lethal portions.

"We are calling for residents to avoid eating fugu, using Gamagori city's emergency wireless system," which broadcasts over loudspeakers located around the city, local official Koji Takayanagi told AFP.

Fugu, an expensive seasonal winter dish, is eaten raw as sashimi or cooked in soup.

The fish's livers, ovaries and skin contain the deadly poison tetrodotoxin and special training and a licence are required to prepare the fish.

There is no antidote to the poison.

Tetrodotoxin affects the nerve system and the poisoning has been described as "rapid and violent", leading to first a numbness around the mouth, then paralysis and eventually death.