Finland's Green League party said Thursday it was leaving the ruling coalition over the approval by the government of a nuclear plant project to be built by Russia's Rosatom.

The Greens oppose the nuclear plant in Pyhaejoki, on the Finnish west coast, which will be operated by Finland's Fennovoima and has obtained a green light from the government.

"I feel heavy-hearted and I'm disappointed... I suggest we quit the government on Saturday," Green League president Ville Niinistoe told a press conference.

The Greens must still ratify the decision through a vote which is considered a formality, given the party's consistent criticism of both nuclear power and the involvement of Rosatom, which will be the plant's supplier and owns 34 percent of Fennovoima.

"This is about choosing to invest in domestic renewable energy... or betting on a nuclear project led by Rosatom, which operates under the rule of the Russian state," Niinistoe said on Monday.

Prime Minister Alexander Stubb said Fennovoima's project was "very important" and rejected the objections sparked by Russia's involvement.

"I understand the concerns, but I want to emphasise that we will act according to Finnish regulations," Stubb said at a press conference.

The government approved the proposal by 10 votes to 7 and has referred it to parliament, which is due to vote on it a second time.

The project has gone through a series of twists and turns in a country that believes in the future of nuclear power.

In July 2013, Fennovoima chose Rosatom to build the plan, despite the company not featuring on a list of possible suppliers in 2010.

In December, Fennovoima announced that a subsidiary of Rosatom, Rusatom Overseas, would take over 34 percent of the company's capital, taking over shares sold by Germany's EON in 2012.

The government wants at least 60 percent of Fennovoima's capital to be in the hands of Finnish or European investors.

With the Greens' departure, the governing coalition will only have 102 seats in Parliament out of a total 200.

In March, the Left Alliance -- another small party -- also quit the coalition government in protest against budget cuts.

The remaining parties in the government will be Prime Minister Alexander Stubb's conservative party, the Social Democrats -- which holds the ministry of finance -- a party representing the Swedish-speaking minority and the Christian Democrats.

The Fennovoima project has also created tension between the parties remaining in the coalition.

Four out of six Social Democratic ministers voted against the proposal, according to Finnish media.

rt/efb/ts/gj

E.ON