UPDATE 1-Finland's Kesko drops out of Fennovoima nuclear project

(Adds comments from Kesko and Fennovoima, background)

HELSINKI, March 27 (Reuters) - Finnish retailer Kesko on Thursday said it would drop out of the Fennovoima nuclear project, adding to concerns over the progress of the consortium's plan to build a 4 to 6 billion euro ($5.5-$8.3 billion) reactor in western Finland.

Kesko, which owned around 2 percent of Fennovoima shares, said it saw increased risks in the project, which is expected to come up for review in parliament in the summer.

"The financial, contractual and schedule prerequisites for the project still contain uncertainties, and it (Kesko) estimates that their risks have increased," the company said in a statement.

With Kesko's exit, Fennovoima's Finnish ownership would drop below the 50 percent of shares required by parliament.

Fennovoima chairman Pekka Ottavainen said while the announcement came as a surprise, he believed the consortium could find new Finnish investors by the summer.

"We are having discussions with several interested companies," Ottavainen said.

The planned reactor, Finland's sixth, is aimed at securing cheaper energy for investors including Finnish industrial firms and municipal utilities. But a weak economy and low energy prices have forced some to reconsider their participation.

Germany's E.ON, originally a top investor, left the consortium in 2012 as part of a broader strategic review. Russian state-owned nuclear firm Rosatom stepped in to take a 34-percent stake, but some 20 smaller owners have also dropped out.

Rosatom will also supply the reactor, which originally was to have been supplied by another firm, according to the project's original permit approved by parliament in 2010.

The multiple changes to the original permit prompted Economy Minister Jan Vapaavuori earlier this month to announce he plans to bring the permit back to the parliament for a review.

"The investment as such would not have been that significant for us... But we considered that there were so many uncertainties around this project that we didn't want to make the investment," said Arja Talma, a senior Vice President of Kesko, declining to elaborate.

The planned plant in Pyhajoki is estimated to begin operating in 2024 and owners, including steel firms Outokumpu and Rautaruukki, are promised electricity at a price of less than 50 euros per megawatt-hour. ($1 = 0.7254 Euros)

(Reporting by Jussi Rosendahle; Editing by Sakari Suoninen and Sonya Hepinstall)