Bolloré, who is also chairman of the Havas advertising network, owner of the Media Planning Group agency, has said continually his interest and purchase of shares in Aegis will not lead to a takeover move.
But the latest increase to 19.1% will fuel speculation that his ongoing purchase of shares will lead to an attempt to gain positions on the board of directors.
The latest twist comes just days after global advertising network Publicis ended its interest in rival media group Aegis after a three-period of behind the scenes negotiations.
The French-based Publicis Groupe said the decision to pull out of negotiations with Aegis, which owns the Carat and Vizeum planning and buying shops, was made after a move to offer what would have been over £1.5bn for the group was said not to be in the best interest of shareholders.
The fourth network involved in the ongoing saga, Sir Martin Sorrell's WPP, confirmed its interest in the group on Friday, but its "primary" interest was in the Synovate market research division of the Aegis empire.