The New York theater where CBS broadcasts its "Late Show" will step up security measures after host David Letterman was threatened at a radical Islamist forum, the online edition of the New York Post said Friday.

A source close to CBS cited by the daily said that next Monday the Ed Sullivan Theater on Broadway near Times Square will have additional security measures in place, while the FBI and the NYPD continue to investigate the threats.

The "Late Show" was not on the air this week because Letterman is on vacation and up to now neither the show host nor the network have commented on the matter.

An individual identified as Omar al-Basrawi urged this week at the Shumukh al-Islam forum that Letterman's tongue be cut out and his neck broken in response to a joke he made about the one-eyed Al Qaeda leader Ilyas Kashmiri, killed in June during an attack by U.S. forces in Pakistan.

Erroneously referring to Letterman as a Jew, the message added that the host "showed his malignant nature and deep hatred for Islam and Muslims when he said that Kashmiri died and joined (Osama) Bin Laden."

Other celebrities have been threatened in the past by radical Islamists, including the creators of the controversial animated television series "South Park," Trey Parker and Matt Stone, who in 2010 received threats on the radical Islamic Web site for dressing up Mohammed as a bear in one of its episodes.