Creos manages electricity and gas network infrastructure in Luxembourg while Enovos is an energy supplier. Both companies form part of Encevo, three quarters of which are directly or indirectly owned by the Luxembourg state, with one quarter owned by China Southern Power Grid International.

Encevo did not reveal the nature of the attack but said that it is currently working on understanding and resolving the incident. A crisis unit was immediately deployed, the company said.

A spokeswoman could not indicate whether any personal data by customers had been compromised. “It’s too early to say anything,” she said, adding that “an analysis is ongoing.”

Encevo is working with Govcert.lu--a national authority on computer-related incidents--Luxembourg’s High Commission for National Protection and the police to investigate the attack and its perpetrators.

The cyberattack occurred in the night from 22 to 23 July. “This attack has a negative impact on the functioning of the client portals of Creos and Enovos,” Encevo said in its statement. “We apologise to our customers for the inconvenience and are doing our best to re-establish the service as quickly as possible.”

The supply of electricity and gas wasn’t affected by the attack.