Hedge fund Citadel Investment Group increased its stake in Gemstar-TV Guide International Inc. to 8.4 percent Thursday and urged the company not to sell to itself to “a financial buyer.”

Gemstar, controlled by Rupert Murdoch, put itself up for sale July 9 and shares have gained more than 30 percent since.

In a letter filed with the Securities and Exchange Commission, Citadel suggested the Los Angeles-based media company consider selling itself to another media company.

“Certain strategic investors may be able to more fully realize the strategic value of Gemstar-TV Guide’s unique assets. “If such investors are willing to recognize the full value of this business, we would be pleased to offer our support for a sale of the company.”

Shares of Gemstar fell 7 cents to $6.66 in afternoon trading Thursday on the Nasdaq.