The son of al-Qaeda founder Osama bin Laden has called on Muslims to independently attack the U.S., Israel, and other countries from the inside.

Hamza bin Laden, 24, issued an audio recording telling Muslims that it “is your duty” to engage in lone wolf attacks—not as part of larger terrorist organizations—within the U.S. and other Western nations, including Israel.

Dubbed the “crown prince of terror,” Hamza bin Laden was with his father when the elder was killed by a U.S. Navy seal team in a Pakistan compound in 2011. The younger bin Laden managed to escape, while his brother Khalid was killed.

Rita Katz, director of the SITE Intelligence Group, tweeted that Hamza bin Laden’s call for independent Muslim terrorism was recorded before June 2015, adding that the recording might be an effort to boost al-Qaeda’s popularity by reviving the bin Laden brand.