According to reports, hackers have demanded ransom from Norway’s Norsk Hydro as part of cyber attack.

Norsk Hydro said on Tuesday it had been hit by a ransom cyber attack of unknown origin, with hackers demanding a ransom.

“The situation is quite grave,” said Norsk Hydro CFO Eivind Kallevik.

“This virus is a so-called encryption virus, also commonly known as ransom virus,” he told a news conference.

Ransom viruses encrypt files using malware that render them unusable. The hackers then demand a ransom to unlock them.

“No sum has been mentioned,” Kallevik said.

He said Norsk Hydro is relying on internal and external resources “to find what you can call a cure for getting this virus out of the system”.

Described as “extensive”, the attack began around midnight (11pm GMT) on Monday. So far it has had only a limited effect on production. All plants were disconnected from the IT system and some were switched to manual mode.

Some plants making aluminium products were impacted on Tuesday, but Hydro’s main aluminium production sites are “running as normal”.

“Our main priority now is to ensure safe operations and limit the operational and financial impact,” Kallevik said.