David Letterman will end his 33-year run as a late-night TV host on Wednesday, May 20, 2015. Reuters

David Letterman has received a death threat from a Jihadist group Web site frequently accessed by Al Qaeda, posting plans to assassinate the "Late Show" host because of an offensive joke.

An explicit assassination threat against Letterman surfaced Wednesday on the Shumukh al-Islam Web site after the late night talk show comedian told a joke about senior Al Qaeda member and lieutenant to Osama bin Laden, Ilyas Kashmiri, according to Entertainment Weekly.

Private intelligence agency SITE tracked and translated the message written by a man named Umar al-Basrawi, which read:

"Is there not amongst you a Sayyid Nosair al-Masri (may Allah release him) to cut the tongue of this lowly Jew and shut it forever. Just as Sayyid (may Allah release him) did with the Jew Kahane."

The Shumukh al-Islam Web forum was reportedly used by Al Qaeda members when they were under America's radar following the September 11 attacks.

"It's a clearing house for Al-Qaeda material," SITE analyst Adam Raisman said in a statement to Entertainment Weekly. "It gets the most Al-Qaeda supporters."

Raisman said this death threat to David Letterman "was a more explicit threat" than the 2010 threat to South Park creators by Revolutionmuslim.com.

David Letterman, referred to as the "lowly Jew" in the post, reportedly offended the extremist group when he spoke of Kashmiri, drawing a slit across his own neck to represent Kasmiri's death by American airstrike back in June.

"He showed his evil nature and deep hatred for Islam and Muslims, and said that Ilyas Kashmiri was killed and he joined bin Laden," the post from the Web site said. "We ask Allah to paralyze his tongue and grant the sincere monotheists his neck."

The SITE group is currently tracking information regarding the post and urged Letterman to be cautious. CBS did not comment on the David Letterman death threat.