Activist investor Carl Icahn has a 9.8 percent stake in Caesars Entertainment and believes the casino operator should explore a sale, according to a Securities and Exchange Commission filing released Tuesday.

The filing, which confirms previous reports that Icahn has taken a stake in the company, said, "Shareholder value might be best served, and enhanced, by selling the company."

Caesars shares jumped to their highs of the day after the filing. They closed up 5.1 percent.

Icahn, according to the filing, thinks the stock is "undervalued" and may nominate "a slate of directors" to the board at Caesars' annual shareholders meeting. "We also intend to have discussions with other stockholders to understand their perspectives and priorities."

The news comes after The Wall Street Journal reported last week that Icahn had taken a stake of roughly 10 percent in Caesars.

Caesars did not immediately respond to CNBC's request for comment.

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