A German man accused of sending threatening letters signed with the acronym of a notorious neo-Nazi group connected to a string of murders and robberies was sentenced to six years in jail.

The 54-year old defendant, identified as Alexander M. due to German privacy laws, will serve five years and 10 months in prison, DPA reported.

A Frankfurt court found the man guilty on multiple charges, including incitement of hatred, disturbing the peace, threats, and the assault of a police officer.

Prosecutors said that Alexander M. texted, faxed, texted and emailed a series of letters to journalists, lawyers and politicians containing threats. They were signed “NSU 2.0.” The acronym is used by a neo-Nazi organization known as the National Socialist Underground (NSU).

NSU was a German neo-Nazi group whose existence was discovered in November 2011. The group was described by Germany’s attorney general as a "right-wing extremist group whose purpose was to kill foreigners, and citizens of foreign origin.”

It has been connected to multiple crimes, including the murders of nine Turkish, Greek and Kurdish immigrants from 2000 to 2006, the murder of a police officer and the attempted murder of her colleagues, several bombings between 1999 and 2004, and 14 bank robberies.