By Anne Kauranen and Essi Lehto

HELSINKI (Reuters) -Nordic utility Fortum faces cyberattacks on a daily basis in Finland and Sweden and has sometimes spotted drones and suspicious individuals near its sites, its CEO told Reuters, adding the company had asked the authorities to investigate.

Security services in Finland and Sweden declined to comment on specific incidents, but both have alleged a pick up in malicious activities by Russia in recent years.

Russia's foreign ministry or embassy in Helsinki did not immediately reply to a written request for comment.

Finland and Sweden angered eastern neighbour Russia by joining the Western military alliance NATO in a foreign policy U-turn after Russia's full-scale invasion of Ukraine in 2022.

"There are different kinds of cyberattack attempts, or cyber security breach attempts, against us daily, and then less frequently, drones and different kinds of suspicious movement around our assets," Fortum CEO Markus Rauramo said, adding power plants' satellite connections were disturbed earlier this year.

Fortum has hydro, wind, solar, nuclear and combined heat and power (CHP) plants.

Rauramo added the situation was broadly similar at Fortum's Swedish assets.

He said Fortum had taken extensive precautions to try to mitigate cyberattacks, including strict access control, private security services, reserve systems, and drills with authorities.

"There has been an uptick in the frequency (of incidents) just as authorities are also reporting. The numbers are increasing, but the impact on our operations is very small," Fortum's head of security Jari Stenius said.

Finland's National Bureau of Investigation KRP told Reuters police had several open investigations on incidents near critical infrastructure, without giving details.

Finland's Security and Intelligence Service Supo and Finnish police declined to comment on the cyberattacks directly, or who might be behind them. Swedish Intelligence Service Sapo also declined to comment on specific incidents or targets.

RUSSIAN SECURITY THREAT

However, a deterioration of relations between Finland and Russia since 2022 has led to an increase in cyberattacks and intelligence operations from Russia, targeting Finland's critical infrastructure, Supo told Reuters, calling Russia the main threat to Finland's national security.

A spokesperson for Sweden's Sapo said: "We have seen a change in security-threatening actions in and against Sweden from Russian intelligence," adding Russian intelligence was more opportunistic, more aggressive and taking bigger risks.

NATO and Western intelligence services including Finland'shave warned that Russia is behind a growing number of hostile activities across the Euro-Atlantic area, ranging from repeated cyberattacks to Moscow-linked arson - which Russia denies.

Russia has threatened Finland with retaliation for joining NATO and seized Fortum's Russian energy assets worth $1.9 billion last year, in response to European Union sanctions.

(Reporting by Anne Kauranen and Essi Lehto, additional reporting by Nora Buli in Oslo and Moscow newsroomEditing by Alexandra Hudson and Mark Potter)