Sweden's financial regulator said on Friday it had requested information from Borse Dubai regarding its move this week to acquire shares in OMX and was considering whether a statement from the state-run firm may already represent an offer to buy all of OMX.

We have asked for information regarding the book building process, how it was conducted, said Annika von Haartman, head of prospectuses and listings at the Financial Supervisory Authority (FSA).

The reason we are doing this is we are actually assessing whether the press release itself can be considered to be a bid, according to Swedish legislation, she told Reuters by telephone.

Von Haartman said it had asked for the information by Tuesday and that, following a conversation with Borse Dubai, it expected the group would cooperate.

Borse Dubai said in a news release on Thursday it was undertaking a book building process to buy shares in OMX at 230 crowns per share. The statement said Borse Dubai's agreements for shares or options meant it was not under an obligation to buy any shares if it did not amass a stake of 25 percent.

OMX has an agreed bid worth about 207 crowns per share, or $3.7 billion, from U.S. exchange Nasdaq.