More than 20 customers had gathered in the Sheung Wan district of the Asian financial hub awaiting the 10:30 a.m. opening time of a conveyor-belt sushi chain, Sushiro, while dozens streamed in by 12 p.m., despite a wait time of an hour.

"I don't feel too concerned about radiation," said one of those in the queue, 22-year-old Verita, who gave only one name."Moderation is key in everything, right? Occasionally dining out (for sushi) ... shouldn't pose a significant risk."

Hong Kong's ban on seafood imports from 10 Japanese regions began on Thursday, with authorities saying it was a precaution to safeguard public health.

Japan started its discharge the same day into the Pacific Ocean, a polarising move that provoked fresh, fierce criticism from China that it was "selfish and irresponsible".

The Chinese-ruled city is permitting food imports from 13 other Japanese regions but they face strict tests and monitoring, with daily radiation levels published online, the government said.

Japan's second largest market for farm and fisheries exports after mainland China, Hong Kong has numerous popular Japanese restaurants, while the country is a favourite holiday destination for many.

Mainland China said it had suspended imports of all aquatic products originating from Japan.

In Hong Kong supermarkets on Friday, sashimi and seafood were clearly labelled with their places of origin, showing that many such items came from Argentina, Canada and Norway.

Billy Tse, 20, who was lining up for his sushi "fix", said Hong Kong people may already be consuming water with some kind of contamination from China's own nuclear emissions.

"I personally wouldn't worry about issues like eating raw seafood from Japan," he added. "Even if Japan discharges nuclear wastewater, I would still come here to dine."

(Reporting by Joyce Zhou and Tyrone Siu; Writing by Farah Master; Editing by Clarence Fernandez)