Finland's biggest energy company Fortum has decided to invest in a major nuclear power project and thus improve its chances of winning approval from the parliament later this week.

Fortum said on Tuesday that it will join Fennovoima project, located in northwestern Finland, with a 15 percent share. The entry of Fortum will satisfy a criteria for parliamentary approval, which requires at least 60 percent domestic or EU ownership.

Finnish Minister for Economy Jan Vapaavuori welcomed the news and said the planned purchase by Fortum assures the level of domestic ownership.

Fortum owns two nuclear power plants in Loviisa, southern Finland, and has a 25 percent stake in another major nuclear power producer Teollisuuden Voima (TVO).

Fennovoima's licence change required additional parliamentary processing due to the switch to Russian technology.

Following an earlier pullout of the German E.ON from the Finnish nuclear power project, Fennovoima opted to use Russian technology and the Russian Rosatom became a major owner.

To get final parliamentary approval, the plant must have at least 60 percent ownership from the EU or the European Economic Area.

The Director General of Rosatom Sergei Kirienko said in a statement that the deal will strengthen cooperation between energy companies in Russia and Finland.