Japan has asked eight countries and regions to block its residents from accessing licensed online casino websites, a government source said Monday. It is a crime in Japan to gamble with overseas-based betting sites, prompting the government to address the issue by urging the operators to cut off access to their sites, many of which are provided in the Japanese language.

Japan has moved to crack down on illegal gambling following media revelations that some professional athletes and celebrities have used online casinos. A police survey estimated that more than 3 million people in the country have gambled online.

The gambling sites, easily accessible via smartphones, are legally operated in some nations but not in Japan. Lotteries and betting on approved races -- horse, bicycle, powerboat and speedway motorcycle -- are the only legal forms of gambling in the country.

Japan has engaged with Canada, Costa Rica, Georgia, Malta, Anjouan Island in the Comoros, Curacao of the Netherlands and the Isle of Man and Gibraltar, both British territories, the source said.

In Japan, a law is expected to be enacted soon to tighten regulations on illegal online gambling by prohibiting websites from directing traffic to casino sites. The government plans to reiterate its request to the eight nations and regions after the bill is passed.

An analysis of 40 online casino sites available in Japanese found that all operators were licensed, with around 70 percent registered in Curacao, a Dutch island territory in the Caribbean. About 1.24 trillion yen ($8.6 billion) is believed to have been spent annually by gamblers in Japan, police said.

Only two of the sites explicitly stated that access from Japan is not permitted. Of the 35 sites confirmed to have been accessed, six had all their traffic from Japan.

As the sites operate legally under foreign licenses, it is difficult for Japan to charge operators with gambling-related offenses. Japanese authorities are cracking down on payment agents and promoters advertising the sites on social media for rewards.