The number of "adult entertainment" telephone services registered with the government has grown 4.5-fold in three years, and such businesses are believed to involve prostitution and provide income for organized crime, the National Police Agency said.

There were 12,251 telephone-based adult service companies as of the end of 2002, according to the NPA, which attributed the surge to an adult entertainment law enacted in 1999 that only requires dispatch operators to register with local authorities before going into business.

Operators of these adult services typically arrange to send female "companions" to locations designated by the customers. Police consider such firms a hotbed of prostitution and a new source of income for underworld groups.

In releasing the registration data, the NPA said it has ordered police to keep a close eye on such dispatch services to detect any illegal activities.

The number of registered dispatchers has jumped since the revised Entertainment Establishments Control Law took effect in April 1999.

The NPA said there were 2,684 operators registered by the end of 1999, 5,425 by the end of 2000 and 8,434 by the end of 2001.

The sharp growth apparently reflects the ease of setting up such services. Unlike adult entertainment shops, "you don't need a shop to go into business, and there is little overhead involved," an NPA official said.

The number of mail-order adult video operators, who also must register under the law, likewise saw rapid growth, rising to 2,015 by the end of December from 462 at the end of 1999, the NPA said.