Billionaire activist investor Carl Icahn has acquired a 9.4 percent stake in Family Dollar and is urging the discount retailer to explore ways to boost its value.

Shares of the Matthews, North Carolina, company are up nearly 10 percent in after-market trading.

In a regulatory filing, Icahn says he owns nearly 10.7 million shares of Family Dollar. Based on its closing price Friday of $60.53, the stake is worth $647.1 million.

Family Dollar's low-income shoppers are still struggling as the economic recovery wears on, and its stock is down in the past year while the broader markets are booming. The company said in April it would close 370 underperforming stores and permanently cut prices on about 1,000 basic items.

Family Dollar Inc. officials weren't immediately available to comment late Friday.