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By Inti Landauro and Gwladys Fouche
PARIS/OSLO, March 11 (Reuters) - European exchange group Euronext on Monday extended its offer for Oslo Bors , while keeping the terms unchanged, as its battle with Nasdaq for control of Norway's stock market operator escalates.
Euronext's offer, due to expire on March 11, is now open until April 1 at 6 pm, Central European time. The terms remain at 158 Norwegian crowns per Oslo Bors share, the price Euronext offered when it raised its bid last month.
New York-based stock market operator Nasdaq had matched Euronext's price last week. Both offers value Oslo Bors at around 6.8 billion Norwegian crowns ($782.9 million).
The bid battle for Oslo Bors, one of the last independent stock market operators, began in December, when Euronext, which operates stock markets in Paris, Amsterdam, Brussels, Lisbon and Dublin, made the first move.
The Norwegian bourse's board's response was to seek new bidders and it encouraged U.S.-based Nasdaq to make a rival offer, which was then supported by the Oslo Bors board and its largest shareholder Norwegian bank DNB.
Paris-based Euronext had initially said it had secured the backing of slightly more than half of Oslo Bors shareholders, who had committed to sell "irrevocably", even in the case of a rival offer.
Oslo Bors's board continues to back Nasdaq, an Oslo Bors spokesman said on Monday. "The extension of the offer does not change the situation. It is the same offer," he said.
DNB, which holds a 20 percent stake in Oslo Bors, is sticking with the Nasdaq offer, a spokesman for DNB said.
Mutual insurance group KLP, Oslo Bors' second-largest shareholder with a 10-percent stake, is also sticking with Nasdaq's offer, a spokeswoman said.
The acquisition of Oslo Bors would diversify Euronext's revenue from shares and derivative trading into seafood derivatives as well as oil services and shipping.
Euronext plans to appoint Oslo Bors's CEO to its managing board, with responsibility for all commodities operations. It said it would also invite a leading figure from the Norwegian financial community to its board.
It has also said it would concentrate all its commodities businesses in Oslo.
Euronext has been looking to expand but remaining opportunities are scarce as market operators either already belong to large groups or want to remain independent.
Large-scale mergers have also met opposition from competition regulators, who have blocked a planned tie-up between Deutsche Boerse and the London Stock Exchange .
$1 = 8.6854 Norwegian crowns Reporting by Sudip Kar-Gupta; Editing by Jane Merriman