The communications ministry in Japan plans to tighten regulations for Internet-Protocol (IP) telephony, after a blackout incident affected millions of customers last month, according to a report.

The ministry also plans to strengthen the maintenance and security of national IP communication networks by and employing more professional engineers to deal the accidents, Japanese daily Asahi Shinbum said Monday.

In May, Nippon Telegraph and Telephone East Corp. (NTT East) and NTT West Corp., Japan’s main IP service providers, reported an accident where 3.18 million fiber optic circuits froze, making IP phone connections impossible for 3 1/2 hours.

The ministry regarded the accident as serious, and it began expanding the list of accidents where IP telephone service providers should notify the ministry.

Current rules require IP telephone service operators to report accidents to the ministry only when 30,000 or more subscribers cannot make phone calls for more than two hours.

For now, minor accidents such as difficulty in connecting to other phones via the Internet or delays in receiving e-mail messages through the Internet don’t have to be reported to the ministry, so the ministry cannot collect data for such accidents directly.

The ministry, however, acknowledges some minor accidents might cause serious disruptions of telephony and other services. If data can be collected on a wider scale, it can be studied and the ministry can offer solutions to prevent recurrences.