NTT Docomo said Thursday that voice calls, mobile data and texting had been unstable across Japan since around 11:18 a.m., affecting some services of other mobile providers that use its network. The carrier was investigating the cause and checking whether emergency calls were affected. Earlier, Docomo suspended its online shop and My docomo customer portal at around 1:05 a.m. after concluding that an outside party had likely gained unauthorized access to its servers. The outage prevented customers from signing up for mobile plans, checking bills or changing contracts, and Docomo said it was unclear whether the suspected unauthorized access was linked to the mobile disruptions.