By Yuka Obayashi
TOKYO (Reuters) -Japanese mobile carrier KDDI Corp said it aimed to restore services by Sunday evening after nationwide network troubles affected up to nearly 40 million users, making calls and getting online difficult for more than a day.
The disruption, which started about 1:35 a.m. on Saturday (1635 GMT Friday), have also affected a wide range of services, from weather data and parcel delivery to banking and transportation that use KDDI networks.
"We deeply regret this as a telecommunications carrier in a position to support critical infrastructure and provide stable services," KDDI President Makoto Takahashi told a news conference, adding that the company takes it as a serious accident.
Around 70% of services have been recovered by mid-morning on Sunday and KDDI plans to recover the rest by around 5:30 p.m. (0830 GMT), Takahashi said.
Up to 39.15 million users have been affected by the failure that occurred after the voice call switch system experienced congestion with data beyond processing capacity, the company said, adding the detailed causes were still been investigated.
The widespread network errors have disrupted transmission of the weather data at the Meteorological Agency, automated teller machines at a regional bank in central Japan and the online system to track the delivery of parcels at Yamato Holdings, according to Kyodo news agency.
KDDI customers flooded Twitter to complain, with one claiming some taxi drivers were not able to take credit cards or electronic payment due to the outage.
The government is investigating the outage.
The incident falls under the category of a serious accident under the telecommunications business act, Yasushi Kaneko, the minister for internal affairs and communications, said on Sunday, adding the ministry will take necessary measures after receiving an official report from the company.
"We take the situation seriously, as emergency calls such as fire and emergency services to protect the lives and property have been hindered at a time when the risk of the pandemic and heat stroke is increasing and a typhoon is approaching," Kaneko told reporters.
The importance of the stability of mobile networks was highlighted by unseasonably hot weather that had sent some elderly people to hospital and with a typhoon heading toward Japan's southern island of Okinawa.
The government is eager to avoid public discontent a week ahead of an upper house election on July 10.
(Reporting by Yuka Obayashi; Additional reporting by Ritsuko Shimizu, Nobuhiro Kubo and David Dolan; Editing by Gerry Doyle and William Mallard)