Economic expansion is prompting Dubai firms to look overseas

Borse Dubai broke the law when it said it planned to buy more than 25%, which would trigger a takeover, the Financial Supervisory Authority said.

But as the firm later rectified its mistake by launching an official $4bn (�2bn) offer no action will be taken.

Borse Dubai is battling against US rival Nasdaq to take over OMX.

Stockholm-based OMX runs the Nordic Exchange, which gives investors access to the biggest firms in Scandinavia and the Baltic states.

Bidding war

Borse Dubai's all cash offer - tabled on 9 August - trumped a $3.7bn recommended cash-and-share offer tabled by the US exchange operator in May.

While the FSA is taking no action, it ruled that Borse Dubai had broken Swedish financial law on two counts - first with its original share purchase announcement and again when it amassed a 10% holding in OMX without applying to the regulator beforehand.

"Borse Dubai has breached the act on takeovers in the stock market," Sweden's FSA said.

"Borse Dubai has subsequently complied with the act. Therefore, no further action will be taken."

Had the FSA ruled against Borse Dubai it could have faced a fine of up to 100m kronor (�7.2m, $14m) fine.