The number of businesses offering on-call sex services to customers at their homes or other locations tripled in the two years since police began regulating such trade in 1999, the National Police Agency said Thursday.

The agency said police counted 10,544 on-call sex firms across the country as of the end of 2001.

Under 1999 revisions to the adult entertainment law, those starting an adult entertainment business must register with local authorities, even if they lack facilities where customers can receive services.

The amended legislation, however, still "allows just about anyone" with limited capital to go into the on-call sex business as it is not subject to location restrictions, an NPA official said.

The new adult entertainment law stipulates three types of adult entertainment firms that operate without customer facilities: Internet providers of adult materials, mail-order providers of adult videos and other types of adult entertainment, and providers of on-call "fashion health" (prostitute) services.

The third is most popular.

While all three categories have registered a marked increase since the new law came into effect, the on-call fashion-health trade has expanded particularly quickly with the number of firms in the sector rising from 2,684 in 1999 to 8,434 in 2001.

By contrast, the number of adult-entertainment facilities such as "soapland" bathhouses -- essentially brothels -- and strip clubs has declined over recent years, falling from about 16,000 in 1985 to 11,000 in 2001, according to NPA figures.

The NPA attributed the drop to tighter local-level regulations.