An audio message purportedly from al Qaeda leader Osama bin Laden threatened retaliation against Americans if alleged 9/11 mastermind Khaled Sheikh Mohammed is executed.

The message -- aired Thursday by the Arabic-language TV network Al-Jazeera -- is directed at "the American people about our prisoners," the speaker said.

"Your master in the White House is following his predecessor in many important issues, like escalating the war in Afghanistan and unfairly treating our prisoners -- led by the hero jihadi Khalid Sheikh Mohammed," who faces trial in the United States for his alleged actions in the 2001 attack.

"The White House declared that they will execute Khaled Sheikh Mohammed and his comrades in arms."

If the United States makes a decision to execute al Qaeda prisoners, "it would be responsible when we execute anyone of you we capture," he threatened.

"We have been enduring your masters' oppression for a long time, especially by supporting Israel's occupation of our land in Palestine. Our reaction to that oppression was heard loudly on the 11th with God's help," a reference to the Sept. 11, 2001 attack on the United States.

"Justice is to be treated in the same manner," he said.

Purported bin Laden messages last surfaced in late January.

In one of them, the al Qaeda leader condemned the United States and other industrial nations for causing climate change. The message criticized former U.S. President George W. Bush for rejecting the Kyoto Protocol on global warming, and the speaker condemned international corporations.

In another, bin Laden claimed responsibility for the alleged Christmas Day attempt by Nigerian national Umar Farouk Abdulmutallab to blow up a Northwest Airlines plane as it approached Detroit, Michigan, from Amsterdam, Netherlands. Bin Laden also warned the United States of more attacks.

CNN could not independently confirm the authenticity of the messages.

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