Bollore, who seized control of French agency holding company Havas in a similar fashion last year, has boosted his holdings in Aegis to 8.89 percent from 8.04 percent. Harris has been buying and selling Aegis shares, but controls 10.56 percent as of its last filing. Harris manages funds that also are big investors in Publicis and may be a factor in Publicis' offer, according to sources with knowledge of the situation. Harris fund manager David Herro is known as an "activist" trader, who has influenced the outcome of agency ownership in the past--most notably helping to depose Maurice and Charles Saatchi from the agency that bears their name, which is now part of Publicis.

Reports have circulated in the past day that Publicis and Aegis had struck a so-called "standstill agreement" that would allow the two companies to work together to help Publicis prepare a friendly offer without the threat of a hostile play. Online U.K. trade publisher Brand Republic published a report early this morning citing anonymous Publicis sources who deny it has entered into due diligence negotiations with Aegis.

Le Figaro, meanwhile, reports that Havas' Bollore might either try to block a sale to Publicis, or might actually sell his shares to Publicis to aid with its bid. It also reported that Bollore is "continuing negotiations" with another rival, U.K.-based WPP Group, about a "key role" in Havas' future.

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