More than 10,000 members of so-called tokuryū criminal groups are believed to have been arrested in Japan in the three years through 2023, a National Police Agency (NPA) survey showed Thursday.

Tokuryū, which means anonymous and fluid, refers to a criminal group whose members are loosely tied and do not know even each other's names. Tokuryū groups are distinguished from conventional gangs and quasi-gangs.

The NPA came up with the first estimate on the number of tokuryū member arrests by subtracting members of known crime syndicates from the total arrests.

Because the survey focused on certain types of crime such as special fraud and drug dealing, the actual figure could be higher, the agency said.

It was specifically found that in the three years 10,378 people believed to be tokuryū members were arrested. Of the total, 6,170 were implicated in special fraud including telephone scams, 2,292 in drug trafficking, 1,721 in "criminal infrastructure" development — such as issuing fake passports, facilitating illegal employment and running underground banks — and 195 in robberies, thefts and other crimes as "part-timers."

The NPA added that these are not exact numbers of tokuryū members because they include suspects who have been regarded as quasi-gangsters while excluding illegal scouting, casino operation and other cases in which identifying such members is difficult.