Finnish power grid operator Fingrid said it started two backup power plants early on Thursday to balance the country's electricity system and thus prevent blackouts.

"Fingrid asked the electricity market for more up-adjustment offers and the situation has been brought under control," it said in a statement.

"The price of adjustment electricity is currently exceptionally high at approximately 5,000 euros/MWh," it added.

The startup of the Huutokoski and Forssa reserve power plants was triggered by an outage at Finland's new Olkiluoto 3 (OL3) nuclear reactor alongside a shortfall of wind power production, a Fingrid spokesperson said. (Reporting by Anna Kauranen, writing by Terje Solsvik, editing by Stine Jacobsen and Anna Ringstrom)