The communications ministry is taking strict action against SoftBank Corp. after its mobile services were disrupted in some parts of Japan on Dec. 6 for about four and a half hours.

As the connection problems constituted a "serious incident" under the law, the ministry plans to give the company administrative guidance and require thorough efforts to take preventive measures.

"It is extremely regrettable that an inconvenience was created for many users nationwide," said communications minister Masatoshi Ishida at a post-Cabinet meeting news conference on Dec. 7. "SoftBank needs to take the incident seriously as a telecommunications carrier providing vital services in people's lives."

The service disruption started around 1:40 p.m.

The ministry has already demanded the company submit a report on the causes of the disruption, according to Ishida.

Under the Telecommunications Business Law, any outage affecting 30,000 or more people for at least one hour is defined as a “serious incident.” The law requires the responsible company to immediately report the incident and then submit a detailed report that includes preventive measures within 30 days.

At the end of September, SoftBank had 33.95 million mobile contracts. The number of users affected by the Dec. 6 incident is yet to be determined, but it is highly likely to exceed the 30,000 threshold.