Investors accuse Citi execs of "suspicious" trades

The shareholders contend that Rubin, former Chief Executive Charles Prince and other current and former executives engaged in "suspicious" stock sales that were "made at times calculated to maximize the personal benefits from undisclosed inside information."

Together, the insiders sold nearly 3 million shares of Citigroup stock at artificially inflated prices for combined proceeds of about $150 million in the period from January 1, 2004, through February 22, 2008, the lawsuit contends. The complaint says the sales "were unusual in timing and/or amount."