The move follows last year's acquisition of 49% of the London advertising agency Mustoes, as Hakuhodo seeks to expand from its Asian roots.
The company is the second largest advertising group in Japan after Dentsu. It has been tipped as one of the few advertising groups in the world that might benefit from buying some or all of the assets of stricken Cordiant Communications, although there have been no reports that it has made an approach.
However, it is known that Hakuhodo is making moves on Dentsu's dominance. In December last year, it announced that, along with the smaller Japanese ad agencies Daiko Advertising and Yomiko Advertising, it would form a holding company that would have billings of around Y1,000bn (£5.2bn).
The deal saw the three agencies operating under one umbrella, as well as the formation of a fourth agency to handle media.
Mendelsohn/Zien will remain majority-owned by its founders Richard Zien and Jordan Mendelsohn, according to the report. The agency's clients include BMW North America and the burger chain Hardees.
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