U.S. banking giant Citigroup won approval from the European Union (EU) Monday to buy Japan's third-largest brokerage firm Nikko Cordial, the biggest ever takeover by a foreign company in Japan.

The European Commission, the EU's antitrust watchdog, cleared the deal under a simplified fast-track approval process after identifying no antitrust problems and receiving no complaints from rivals within 25 working days.

Citigroup announced a takeover bid worth 10.8 billion U.S. dollars for Nikko Cordial in March, aiming to buy a controlling stake of at least half of the shares of the Japanese brokerage, which was hit by an accounting scandal last year.

Acquiring Nikko would also give Citigroup a bigger piece of the market for managing the huge pool of private savings in Japan, valued by some at up to 17 trillion dollars.

The deal would create a new financial giant in Japan with the know-how and financial power to challenge longtime market leaders in the country like Nomura Holdings and Mizuho Financial Group.

Citigroup's move would be the latest in a string of acquisitions of Japanese companies by overseas buyers that has underscored the extent to which Japan's once tightly closed economy has opened to the world.