Police in Frankfurt have arrested an Irish man claimed he was going to commit an unspecified attack in a letter.
The man, 53, was known to authorities for some time leading up to his arrest.
Police say he has sent a large number of handwritten letters to authorities and courts in the state of Hessen in which he would allege injustices on the part of government agencies.
The letters are said to have often been filled with confused and incomprehensible content.
Police believe the contents of the letters indicate an individual suffering from mental confusion. The accused man also cited Nazi-era terms such as Reichsbürger.
The situation escalated on July 12, when the man sent identical letters to several authorities announcing he would carry out an unspecified attack on July 20.
An investigation was launched and a search for the man, whose whereabouts were unknown for some time, was carried out.
The suspect was tracked down at a large garden plot in northern Frankfurt where it is believed he had been staying for a long period of time.
He was arrested and authorities carried out a search of the land as well as a construction trailer, several steel containers and some rundown vehicles which were on the site.
During the course of the search, numerous weapons were discovered including gas, air guns, a crossbow, daggers and swords.
The weapons were seized and the man is being detained and expected to be charged with offences against the German state.