The chief executive officer of Deutsche Boerse AG, Carsten Kengeter, pictured at the German stock exchange's annual general meeting at Jahrhunderthalle on May 11, 2016 in Frankfurt am Main, Germany.

Deutsche Boerse's embattled chief executive Carsten Kengeter is stepping down amid continuing allegations of insider trading, the German exchange operator announced on Thursday.

The decision came at an extraordinary meeting of the supervisory board. No successor was named, and Kengeter will stay on until there's a transition plan.

Deutsche Boerse said that the resignation was "in order to allow the company to focus its energy back onto clients, business and growth and to avoid further burdens caused by the ongoing investigation".

Kengeter and Deutsche Boerse have been dogged by an insider trading investigation since early this year.

The probe stems from shares Kengeter bought in December 2015, just months before formal merger talks with London Stock Exchange were announced.

The shares soared and investigators have been looking into whether Kengeter was already in merger talks before he bought his shares. The merger eventually failed.

Kengeter and Deutsche Boerse have denied wrongdoing.

Kengeter's position became more tenuous earlier this week when a Frankfurt court ruled against a settlement that would have helped him and Deutsche Boerse put the case behind them.

The resignation means two top exchanges will be seeking new chiefs. Last week, Xavier Rolet, chief executive of the London Stock Exchange Group, said he would step down at the end of next year.

Deutsche Boerse and LSE, which had sought to merge, are now competing for market share in the run-up to Britain's exit from the European Union.