Russian state-owned oil giant OAO Rosneft (ROSN.RS) Monday said it offered to buy a combined 21% stake in refinery Saras SpA (SRS.MI) for a total 273.5 million euros ($358.3 million), as Russian companies expand into the ailing Italian refining market.

Rosneft offered to buy 7.3% of Saras at a price of EUR1.37 a share for a total of EUR94.96 million, said the Russian company in a statement published by Italian securities' regulator Consob.

The statement also said that Saras' controlling shareholders--the Moratti family--agreed to sell a 13.7% stake in the Sardinia-based refinery for EUR178.5 million.

Saras shares were suspended from trading earlier Monday, pending the statement, at EUR0.96 each, giving the company a total market value of EUR928 million.

Saras is
Italy 's biggest independent refinery by capacity.

"We believe that this transaction is an important step in building a long-lasting cooperation between Rosneft and Saras," said Rosneft Chairman Igor Sechin in a statement issued by the Italian refiner.

The Saras family will keep a 50.02% holding in Saras after its stake sale to Rosneft, it added.