LISBON (Reuters) - Vodafone's Portuguese unit said on Tuesday a hacker attack overnight had disrupted its services but assured its customers that their personal data had not been compromised as a result of the incident, which is under investigation.
Vodafone Portugal said in a statement its system faced technical problems on Monday evening, with thousands of customers reporting they were unable to make calls or access the internet on their phones or computers.
It later discovered the technical issues were caused by what it described as a "deliberate and malicious" cyber attack.
"There is no evidence customer data has been accessed or compromised," it said. "An in-depth investigation of the criminal act...will continue for an indefinite period, with the involvement of the competent authorities."
The attack on Vodafone came a month after the websites of one of Portugal's biggest newspapers and of a major broadcaster were hacked. Both media organisations remain unable to access their websites.
Vodafone Portugal said it was "determined to restore the normality of services" and mobile use was gradually recovering. The 4G network remains unavailable but customers in most of the country can use 3G.
(Reporting by Catarina Demony; Editing by Andrei Khalip, Kirsten Donovan)