Blowfish for sale at Tsukiji market in Tokyo
© AFP/JIJI Press/File

TOKYO (AFP) - "The three men remain hospitalised. They are heavily poisoned and their consciousness has been impaired," said a police official in northern Yamagata prefecture.

A group of seven men reported feeling numb on Monday soon after eating the testes of "fugu" blowfish, which is highly prized in Japan but is supposed to be prepared only by specially trained chefs because of its potential risk.

Northern Japan is known for imposing less stringent rules on fugu than Japan's culinary hubs of Tokyo and Kyoto.

The diners ate raw meat and baked testes of blowfish at a restaurant in Tsuruoka, an old castle town by the Sea of Japan (East Sea), 350 kilometres (220 miles) north of Tokyo.

The restaurant's owner as in police custody. Media reports said he was a former fisherman who did not have a proper licence to prepare fugu.

The victims, some of whom were understood to be frequent visitors to the restaurant, were offered the fugu dishes by the owner as off-the-menu specials for the winter season.

©AFP