People travelling to Japan are being urged not to bring back aquatic products from parts of the country that are subject to an incoming ban, environment secretary Tse Chin-wan said on Wednesday.

Souvenirs or gifts not for commercial use are not covered by the ban, but Tse said they may pose health risks.

Hong Kong is set to restrict the import of aquatic products from 10 Japanese prefectures from Thursday when Tokyo starts releasing wastewater from the tsunami-stricken Fukushima nuclear power plant.

The 10 prefectures are Fukushima, Tokyo, Chiba, Tochigi, Ibaraki, Gunma, Miyagi, Niigata, Nagano and Saitama. The ban covers all live, chilled, frozen and dried sea products, sea salt and seaweed.

"Our regulation only covers imports for sale, or for other commercial purposes. Individuals who bring a small amount of products back to Hong Kong are not subject to the control measure," Tse told an RTHK programme.

"However, I must make it clear to the public that aquatic products from these areas may have radioactive issues and risks. So I will suggest people don't bring sea products from these places back to Hong Kong."

The chairman of the Hong Kong Japanese Food and Cuisine Association said the ban will give the perception that the entire Japanese food industry is at risk.

"The major impact will be people losing confidence in Japanese food, people don't go to eat Japanese food, they don't walk into Japanese restaurants, and that's what we are very worried about," Dennis Wu told RTHK's Hong Kong Today programme.

He added that some supermarkets had already seen sales of sashimi plunge in recent months.

Wu said he expects a drop in business of at least 20 to 30 percent from restaurants after the restrictions take effect.

But he also said the restrictions would not have a huge impact on the supply and price of sea product imports, as business operators could find alternatives from other parts of Japan.