A jihadist website threatened David Letterman, saying that his tongue should be cut out and he should be killed for making a joke about an al Qaeda leader’s death in Pakistan.

The Muslim extremist website posted a message translated as: "Cut the tongue of this lowly Jew and shut it forever,” said the SITE Intelligence Group.

According to SITE, the death threat against Letterman – who is not Jewish – was posted on Tuesday, on a website used by Muslim militants, after the comedian make a joke about Ilyas Kashmiri, who is believed to have been killed in an airstrike in Pakistan.

Letterman said that Kashmiri would now be joining Osama bin Laden.

SITE released a translation today revealing that a post on the jihad site read: "Is there not amongst you a Sayyid Nosair al-Masri to cut the tongue of this lowly Jew and shut it forever?"

In 1990, Sayyid Nosair al-Masri assassinated radical right-wing Rabbi Meir Kahane in New York.

Broadcaster CBS and Letterman’s spokesperson both declined to comment on the death threat.

However the FBI are looking into the threat.

Tim Flannely, an FBI spokesman in New York, said: "The FBI takes all threats seriously and we will run it down like we do all threats.”

SITE provides information on jihad by monitoring web and print publications. Get more info here: news.siteintelgroup.com