Exchange owner OMX wrote to a Swedish regulator saying it had not tried to interfere with Borse Dubai's takeover bid, according to a copy of the letter provided to Reuters on Friday.

Sweden's Financial Supervisory Authority (FI), which announced this week it was investigating whether OMX had used inappropriate defense measures, provided a copy of the letter. A small part of the letter was blanked out.

OMX legal counsel Magnus Billing, in a letter date Sept. 6, detailed when OMX had contacted Borse Dubai representatives before and after the state-run Dubai firm announced a full bid of 230 crowns per share, or $4 billion, on Aug. 17.

OMX said it had contacted HSBC, a Borse Dubai adviser, on Aug. 9 to find out who at the bank was involved with an initial book-building process and what the intent was.

On Aug. 17, when the offer was announced, OMX said it had contacted Borse Dubai's media relations firm, Hill & Knowlton, to find out whether a news conference was being held.

OMX also said it had contacted Swedish law firm Lindahl about a Lindahl employee advising Borse Dubai. OMX has complained to Swedish Bar Association about the legal adviser because he had recently worked for OMX.

Apart from the above-mentioned contacts, neither OMX nor any of its advisers have contacted advisers of Borse Dubai, the letter said. OMX has thus not taken any actions aimed at damaging the conditions for Borse Dubai's public offer.

Borse Dubai is locked in a takeover battle for OMX with U.S. exchange Nasdaq , which has a cash and shares offer currently valuing the firm at $3.7 billion.

OMX owns exchanges in the Nordic and Baltic region. Borse Dubai is a holding company for the Dubai government's stakes in Dubai Financial Market and the Dubai International Financial Exchange.