"The extraordinary situation in the European economy and energy market is causing market uncertainty and a decline in demand for our aluminium products," Hydro said.

The combined cuts at Karmoey and Husnes correspond to an annual production capacity reduction of 110,000-130,000 tonnes of primary aluminium, including production recently taken out for ordinary maintenance and not yet restarted, Hydro said.

Hydro's Norwegian plants produce just over 1 million tonnes of aluminium annually, according to a company spokesperson.

"Even if 50% of Europe's primary aluminium production capacity has been curtailed during the last year, (the) recent drop in demand is causing a buildup of stock, forcing us to take firm actions," the company added.

The curtailment will lead to a power consumption reduction of around 170-200 megawatts once it is in full effect at the end of 2022.

There will be no staffing changes at the affected plants, and the company will bring forward investment plans during the curtailment period, the company said.

"Underlying market trends longer-term will remain positive due to the rising need for aluminium in support of the European green transition," Hydro said.

(Reporting by Terje Solsvik; Editing by Gwladys Fouche and Josie Kao)