Shares in some of Japan’s most popular sushi restaurants have plummeted after incidents of “sushi terrorism” were published online.

Several videos of customers interfering with food and pranking other diners in some of Japan‘s conveyor-belt sushi restaurants, known as kaitenzushi, have emerged on social media in recent weeks, sparking outrage.

One of the most shared videos, viewed more than 40 million times, shows a young man licking the open top of a communal soy sauce bottle and the rim of a teacup which he then places on a stack of clean cups.

He goes on to lick his finger and touch two pieces of sushi, believed to be for another customer, in the 48-second video.

Other videos show people putting wasabi on other customers’ sushi and licking a communal spoon from a container of green tea powder.

While the culinary criminal in the video and his parents have both apologised, stocks in the Sushiro chain where the video was filmed plummeted by nearly 5% on Tuesday, the Guardian reported.

The company said it intends to pursue civil and criminal proceedings.

Two other chains, Hama Sushi and Kura Sushi, have said they also plan to take legal action and will install cameras above conveyor belts to monitor diners.

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Sushiro announced it has replaced all soy sauce bottles and cleaned all the cups in its branches. It is also asking customers to collect condiments and utensils from a serving point rather than placing the items on individual tables.

The videos of “sushi terrorism” have caused outrage in Japan, a country with high standards of hygiene where the sushi industry is worth £4.7bn.