Five directors of media giant Viacom, including chairman and chief executive Philippe Dauman, were replaced Thursday as the daughter of the elderly company owner Sumner Redstone strengthened her control.

Amid ongoing questions over whether the 93-year-old Redstone is mentally competent to sign off on major corporate moves, his National Amusements Inc, which has 80 percent control of Viacom, announced five new board members to the company.

Also replaced was director George Abrams, who together with Dauman was removed a month ago from the board of the Redstone family trust, in the first major move in the fight between them and Shari Redstone over her father's media empire.

Both are longtime confidants of Sumner Redstone and have alleged in court that Shari Redstone has isolated her father in order to take power in Viacom, where she is vice chair.

In a statement, National Amusements said the new directors, most of them executives with experience in the entertainment and media industry, "have deep experience in corporate governance of public companies and will provide valuable expertise to Viacom."
At least some of the names, including former Sony president Nicole Seligman, are widely reported to be close to Shari Redstone.

The move came after media reports said Sumner Redstone had written a letter to another of the removed Viacom board members, Frederic Salerno, saying he no longer backs Dauman or his allies.

"I no longer trust Philippe or those who support him," Redstone wrote, according to The New York Times.

On Thursday Salerno branded the latest move a "brazen and demonstrably invalid attempt" by Shari Redstone to take over the $40 billion entertainment business, which controls hit names like MTV, Nickelodeon, and Comedy Central, as well as Hollywood giant Paramount Pictures. 

Dauman, Abrams and Salerno maintain that Sumner Redstone's longtime wishes were for the company to be guided by independent and professional management rather than family members when he dies.

However, Salerno said in his statement Thursday, "It is now clear that Mr. Redstone is being manipulated and used by his daughter in an attempt to accomplish her long-held goal of gaining complete control of Viacom."

Dauman and Abrams have asked a Massachusetts court to reverse their removal from the Redstone family trust, and to order a medical examination of Sumner Redstone to show he is not making the decisions, which they attribute to his daughter.

"He is a 93-year-old man suffering from overwhelming physical ailments, including an inability to speak, stand, walk, eat, write or read," they alleged in a court filing.