The recent liberalization of international Internet telephone services is leading to a variety of rates and a mushrooming of service operators.

This development is seen by many as a prelude to further competition later this year in Japan's 470 billion yen international telephone market. In late August, the Posts and Telecommunications Ministry deregulated Internet-based telephone services for international calls, triggering the entry of unconventional service providers into the market.

Two days after the announcement, Chiyoda Corp., a Tokyo-based call-back service provider, started Internet telephone service from Japan to 230 countries. It started domestic Internet telephone service in June. "Venture businesses have the advantage (over existing carriers) because we use a leased telephone line and do not need large-scale investment," Chiyoda President Tetsuji Yamada said. "We can offer the service at much lower costs than existing carriers."

Chiyoda charges 75 yen per three minutes for a daytime weekday call from Japan to the U.S., 83 percent less than the regular rate offered by KDD, the country's largest international carrier. Rimnet Corp., a Tokyo-based Internet provider, started Internet telephone service this month from Tokyo, Osaka, Fukuoka, Nagoya, Yokohama and Sapporo to the U.S. for its member customers.

The company charges 90 yen for the first three minutes and 30 yen per additional minute. It offers the service from 8 a.m. to 9 p.m. only on weekdays. The low charges are possible by using bargain-rate Internet circuits leased by the three existing international carriers, KDD, International Telecom Japan Inc. and International Digital Communications Inc.

The ministry had frowned on the commercial transmission of voice data over the Internet due to the potential impact on existing carriers but later reached the conclusion that the threat is minimal due to limits on the origin and destination of these calls. Chiyoda and Rimnet have access points only in large cities. Callers from other areas can still use the service but must pay the long-distance charge to the access point.

In addition to venture businesses and call-back companies, large firms are also ready to offer Internet telephone services. AT&T Jens Corp., a joint venture of AT&T and Japanese carriers, launched Net phone services earlier this month. Customers can call from Osaka and Tokyo to 36 countries, covering Europe, Asia, the Pacific region, and North and South America. NTT Data Corp. plans to offer the service by the end of this month in cooperation with Softbank Corp. and Marubeni Corp.