Japanese mobile operator NTT Docomo said its international roaming services for subscribers traveling outside Japan were disrupted since Monday evening across 220 countries and regions.
The Nikkei reported Wednesday that problems with voice calls and e-mail services started at 6.24pm Monday Japan time and continued until Tuesday evening. The issue was finally fully resolved just after 10pm on Tuesday night.
Docomo, Japan's largest mobile carrier, said its latest disruption was caused by a network overload, and not equipment failure. It added that a spike in data volume and the number of overseas travelers during the summer holidays were possible factors.
The company received more than 1,300 complaints and inquires, the Nikkei said.
The affected international roaming services follow a similar disruption suffered by Docomo earlier this month. Its communication control servers failed due to an equipment glitch, disrupting service for 1.52 million subscribers both in Japan and overseas, the report said.
A series of major service disruptions from last year to January this year led the company to conduct a review of its equipment and personnel in February and March--which concluded that its network was stable. However, Docomo's senior executive vice president, Fumio Iwasaki, acknowledged that the review was insufficient, after disruptions earlier this month, according to the report.