The PKK terror group collects €25 million (over $28 million) annually in donations from across Europe, Germany's domestic intelligence service said in its report released on Tuesday.
The group, which is listed as a terrorist organization by the European Union (EU), has collected more than €13 million (over $14 million) in Germany alone, between September 2015 and early 2016, according to the Federal Office for the Protection of the Constitution, or BfV.
"The PKK managed to double its revenues from donations in Germany within the last 10 years," the report said.
Germany outlawed the PKK in 1993, but Turkey authorities have been reluctant to take strong measures against the funding, propaganda and recruitment activities of the group, despite repeated warnings from Turkey.
Berlin's reluctance in combatting PKK activities in the country has been the source of major friction between Turkey and Germany.
BfV's annual report said the terrorist group had nearly 14,000 followers in Germany and had recently increased its recruitment activities, sending dozens to camps in northern Iraq.
It also warned that PKK followers may again employ violence in Germany.
"Though largely peaceful events prevail in Europe, violence remains an option of the PKK ideology," the report said.
"The PKK continues to be able and prepared, if necessary, to use violence in Germany at least in isolated cases or to tolerate acts of violence carried out by its young adherents."
German Foreign Minister Sigmar Gabriel has admitted Germany's failures in combating propaganda activities of the PKK terror group in the European country.
"I think Turkey is right when it warns us and says we should not allow the PKK to carry out propaganda activities in public," Gabriel told reporters in a news conference at the Foreign Ministry last Friday.
"I also think that it is unacceptable to ban public appearances of Turkish politicians, but at the same time [we] allow posters of Mr. Öcalan," he said, referring to rallies of PKK followers in Germany, in which they use flags of the PKK and PYD terrorist groups and its so-called chief, Abdullah Öcalan.
Germany outlawed the PKK in 1993, but authorities have been reluctant to take strong measures against the propaganda, funding and recruitment activities of the group, which is also listed as a terrorist organization by the EU and the U.S.
Berlin's reluctance in combating PKK activities in the country has been the source of major dispute between Turkey and Germany, and the issue was recently raised by President Recep Tayyip Erdoğan during his meeting with Gabriel in Ankara early this month.
German courts opened more than 4,000 cases against PKK suspects since 1993, but German authorities often turned down extradition demands by Ankara.
Listed as a terrorist organization by the U.S. and the EU, the PKK resumed its armed campaign against the Turkish state in July 2015, unilaterally violating the cease-fire.
Since then, over 600 security personnel, including troops, police officers and village guards, have died in PKK attacks and more than 7,000 terrorists have been killed during operations across Turkey and northern Iraq, according to the military.