OSAKA (Kyodo) -- A record-high 279 people were accused by Japanese police of using online casinos in 2024, more than twice the number a year earlier, according to preliminary government data, with many apparently unaware that internet gambling is illegal.

Police have been able to track down more users of online gambling sites by looking at the bank accounts of the businesses handling bets in Japan, an investigative source said. But the source added the data represents "only a small fraction of the real figure," with the number of online casino gamblers estimated at 3 million.

Gambling is illegal in Japan even if an online casino is operating legally overseas. Mediators earn fees from overseas casino operators for providing gambling points in exchange for cash or cryptocurrencies, according to the investigative source.

According to the National Police Agency, many of the people accused gambled on their smartphones, with 80 percent, or 227, visiting virtual casinos via their personal electronic devices rather than illegal establishments that provide computer access.

In 2023, a total of 107 people were alleged by police to have used online casinos.

Public awareness of the illegality of online gambling remains low, experts say, with over 100 websites for virtual casinos, some promoted by celebrities, targeted at players in Japan.

A 34-year-old man living in western Japan said he only learned that online casino gambling was illegal three years after he began betting. He remained addicted to gambling on his smartphone despite building up a debt of over 10 million yen ($66,000).

In Japan, individuals face fines of up to 500,000 yen for gambling, with prison terms of up to 3 years for habitual gamblers.

Several entertainers from Japanese comedy giant Yoshimoto Kogyo Holdings Co. have been questioned by Tokyo police on suspicion of gambling through an online casino, another investigative source said Saturday.

Earlier this month, Yoshimoto said some of its entertainers were on hiatus over suspected compliance violations identified in an external legal review amid media reports alleging online casino gambling.