The United States added German former rapper Denis Cuspert to its list of "terrorists" over his role as a fighter with the Islamic State group in Syria and Iraq, the State Department said Monday.

The 39-year-old, who used to rap in Berlin and now goes by the name Abu Talha al-Almani, is one of the most famous Western fighters for IS. He is already listed as an Al-Qaeda supporterbythe United Nations.

The US listing as a "global terrorist" freezes all of Cuspert's assets under US control and prohibits transactions with him.

Cuspertjoined IS in 2012 and has appeared in numerous videos from the group, including one in November "in which he appears holding a severedhead heclaims belongs to a man executed for opposing ISIL (IS)," the State Department said.

The rise of foreign fighters in the ranks of IS has alarmed many Western nations.

"Cuspertis emblematic of the type of foreign recruit ISIL seeks for its ranks -– individuals who have engaged in criminal activity in their home countries who then travel to Iraq and Syria to commit far worse crimes against the people of those countries," the State Department said.

Cusperthas pledged an oath of loyalty to IS leader Abu Bakr al-Baghdadi and is a chief recruiter of German fighters.

German prosecutors have launched an investigation intoCuspertas well as other foreign fighters.