The Interior Ministry fears plans of Paris-like attacks by jihadis in Germany, according to the "Bild" newspaper. Documents said an attack could take place "at any time."
Germany's mass-market paper "Bild" on Thursday reported that the Interior Ministry's confidential security appraisal warned that German state and civilian institutions, their employees as well as civilians could become targets of attacks spread over several days and locations.
"Germany is the avowed and actual target of jihadi-motivated violence," "Bild" wrote, quoting the Ministry's document and went on to cite the report as saying this potential attacks could materialize at "any time."
The greatest danger was posed, the paper quoted the Interior Ministry document as saying, by former combatants of organizations such as "Islamic State" (IS) who had returned to Germany. IS controls a swath of northern Syria and western Iraq.
More than 300 people have returned to Germany after fighting in Syria and were regarded by intelligence services as "battle-hardened and completely brutalized," it said.
In addition Germany's Federal Criminal Police (BKA) was monitoring 420 people regarded as dangerous and prone to violence.
Do more, urges US defense head Carter
On Wednesday, US Defense Secretary Ash Carter, visiting troops in the US state of Kentucky, said his counterparts from seven nations, mainly from Europe, had been invited to talks in Paris next week to discuss ways to defeat IS.
Carter said he would meet with defense leaders from France, Australia, Germany, Italy, the Netherlands and the United Kingdom, and "will not hesitate to engage and challenge" them to get them to do more.
"Each of these nations has a significant stake in completing the destruction of this evil organization, and we must include all of the capabilities they can bring to the field," Carter said.