EURONEXT N.V. 
U.S. stock market operator Nasdaq revealed last week that it would offer 152 Norwegian crowns ($17.98) per share for Oslo Bors, outbidding Euronext. Nasdaq formally made its offer early on Monday.
As it did, Euronext, which had offered in late December to pay 145 crowns per share, valuing the company at 6.24 billion crowns or $739 million, said it might submit a new bid.
"Euronext will assess options to adjust its offer and will communicate when appropriate," the Paris-listed company said in a statement.
Olso Bors' CEO Bente Landsnes said that Nasdaq's offer was better than the one filed by Euronext.
The bidding battle for one of the last independent stock markets in northern Europe reflects consolidation across the industry.
While Nasdaq has the backing of Oslo Bors's management and its largest shareholder, Norwegian bank DNB, Euronext has the support of a narrow majority of the Norwegian exchange's shareholders.
Those shareholders had committed "irrevocably" to tender their shares at the offered price even if a higher rival offer came out.
For Nasdaq to win control it would need either Norwegian regulators to back its bid over Euronext's or for the shareholders who committed to Euronext to let their commitments lapse, which could happen from August, Nasdaq Nordic CEO Lauri Rosendahl told Reuters.
Even with the support of a majority of Oslo Bors's shareholders, Euronext may decide to raise its offer to fend off Nasdaq.
Euronext was invited to bid for the company by a group of Oslo Bors shareholders without informing the company's management.
When the acquisition attempt was made public, the board of Oslo Bors said it would look to the market for a rival bid to make sure shareholders would get the best deal.
Euronext, which runs exchanges in Paris, Brussels, Amsterdam, Lisbon and Dublin, is looking to expand its portfolio but remaining opportunities are scarce as market operators either already belong to large groups or because their shareholders 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.
For Euronext, expansion into Norway would help diversify its revenue from share and derivative trading, given Oslo Bors's leading position in seafood derivatives as well as oil services and shipping.
Euronext's largest shareholders back the takeover attempt, the company's said.
($1 = 8.4455 Norwegian crowns)
(Reporting by Inti Landauro, Sudip Kar-Gupta; additional reporting by Terje Solsvik; editing by Louise Heavens and Jason Neely)
By Inti Landauro and Gwladys Fouche
