Sedmoi Kontinent, the country's sixth-largest food retailer, climbed the most ever in Moscow trading after Kommersant reported that France's Carrefour agreed to buy a controlling stake.

Carrefour, Europe's biggest retailer, signed a preliminary agreement to buy 75 percent of Sedmoi Kontinent and 95 percent of its MCapital unit, which controls most of the company's real estate, the newspaper said, citing unidentified bankers.

The Russian grocery chain's shares soared as much as 30 percent, bringing its market value to about $650 million. Helene Saint-Raymond, a spokeswoman for Carrefour, declined to comment. Vlada Baranova, a spokeswoman with Sedmoi Kontinent, said the Russian retailer did not know anything about a takeover agreement.

Press reports have said Carrefour has considered a bid for the Moscow-based company since February. Sedmoi Kontinent last week offered its bondholders a debt swap to prevent a cash shortage in June, a move that analysts said could be a precursor to a sale.

"Russia is still growing faster than Western Europe," said James Monro, an analyst at Standard & Poor's. "Carrefour still has the cash flow to expand through acquisitions, and now is a good time to buy if you have the money."

Sedmoi Kontinent's intraday gain was the steepest since the company sold shares to the public four years ago. The stock closed up 30 percent at 318.76 rubles on the MICEX on Tuesday.

Kommersant said Carrefour would make its final offer May 15, when it has finished evaluating the retailer's assets. In February, the newspaper said Carrefour offered $1.25 billion, including the assumption of $600 million of debt.