Pan-European stock market operator Euronext, which runs the Dublin Stock Exchange, said today it may sweeten its offer for Oslo Bors as stock market operator Nasdaq made a rival bid. 

"Euronext will assess available options to adjust its offer and will communicate when appropriate," the Paris-listed market operator said today. 

Euronext's announcement comes as US-based stock market operator Nasdaq was due to file a slightly higher bid for Oslo Bors than the one originally filed by Euronext in late December. 

Euronext had offered to pay 145 Norwegian crowns ($17.17) per share for Oslo Bors, which valued the company at 6.24 billion crowns or $739m. 

Last week, Nasdaq said it would offer 152 crowns per share. 

A bidding war for one of the last independent stock market in Northern Europe is a sign the consolidation in the stock market groups in the region is speeding up. 

Euronext runs exchanges in Paris, Dublin, Brussels, Amsterdam and Lisbon.

It 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 previously blocked a planned tie-up between Deutsche Boerse and the London Stock Exchange. 

Even though a slim majority of the Norwegian bourse's shareholders have already committed to sell to Euronext at the price offered, the Paris-based company may decide to sweeten its offer to fend off Nasdaq, a source close to the matter said last week. 

Euronext also said its shareholders have approved a takeover of Oslo Bors. 

Euronext was invited to bid for the company by a group of Olso Bors's shareholders without the support of the company's board. 

When the acquisition attempt was made public, Oslo Bors's board said it would look to the market for a rival bid to make sure shareholders would get the best deal. 

For Euronext, a deal would match its strategy of bolt-on acquisitions. 

An expansion into Norway would help diversify its revenues from share and derivative trading, given Oslo Bors's leading position in seafood derivatives as well as oil services and shipping.