KDDI mobile customers across Japan hit by prolonged network troubles

KDDI Corp, one of Japan's top three carriers, said Saturday its mobile customers have been facing difficulties making calls and getting online for over half a day, with the disruption of its nationwide networks also impacting services from banking and transmission of weather data to parcel deliveries.

The au mobile brand operator said work to restore the networks continues after the disruption began at around 1:35 a.m., but no time frame for a resumption of services has been provided.

The trouble, which the company said is due to a failure with its voice call system, has also affected its low-cost UQ Mobile brand and its lower-priced "povo" wireless customers, as well as other firms using KDDI's networks.

KDDI apologized and said it is still investigating the number of users who complained about being inconvenienced. As of March, its infrastructure has around 62 million mobile subscriptions, with individual contracts for the au, UQ Mobile and povo brands accounting for about 31 million users.

The communications ministry has yet to classify the disruption as a "serious incident." Japan's telecommunications business law stipulates that the government can apply the label requiring a report on the issue's cause within 30 days if 30,000 people or more cannot dial emergency numbers such as 110 or 119 for an hour or longer.

Users of Rakuten Mobile Inc and Jcom Co's low-cost mobile services have also been affected as their services use KDDI's lines.