Redstone increased his stake in Viacom to 8.7%.

A group led by Sumner Redstone, president of Dedham, Mass.-based National Amusements, increased its holdings from the 6.2% reported last June. A Viacom International spokesman was not immediately available for comment, but the company said last June that it believed Redstone purchased his shares on a friendly basis. Last May, New York investor Carl C. Icahn acquired 17% of Viacom’s shares before selling the block back to the company at an estimated $21 million profit.