elliottActivist hedge fund Elliott Management said in an SEC filing it has built up a 6.7% stake in Interpublic in a bid to "engage in a constructive dialog" with IPG's board "regarding steps to maximize shareholder value."

The fund of financier Paul Singer said it is buying the stock on the "belief that such securities are undervalued and represent an attractive investment opportunity."

The No. 4 marketing conglomerate this week reported strong second quarter earnings, including a 10.9% jump in its PR operations to $355.4M. It has been the subject of takeover speculation in the wake of Omnicom and Publicis' attempted $35B tie-up.

The Financial Times reported that Elliott wants Interpublic to explore a sale of the entire business to one of its rivals, including Publicis, Omnicom, WPP, Dentsu or Havas.

IPG's PR firms include Weber Shandwick and Golin, among others.

IPG shares were up 2% in afternoon trading to $20.15.