Tom Freston, president and CEO of Viacom, has resigned effective immediately, the company announced today.

Freston took the helm of Viacom following its split from CBS at the beginning of the year. He oversaw operations at MTV Networks and Paramount. Freston will be replaced by board member Philippe Dauman, who is a close associate of Viacom executive chairman and founder Sumner Redstone, writes Mediaweek. The company also appointed Thomas Dooley chief administrative officer.

Freston's departure comes just weeks after Redstone fired Tom Cruise (though Cruise claimed he quit to join hedge fund backers). The split was said to have undermined management at Viacom and its Paramount studio, writes TheStreet.com.

Viacom shares have fallen since its split with CBS.