Turkish President Tayyip Erdogan on August 7 accused Germany of assisting "terrorists" by not responding to thousands of files sent to Berlin or handing over suspects wanted by Turkish authorities.

“Germany is abetting terrorists,” Erdogan told a conference in the Black Sea province of Rize, in comments likely to further escalate tensions between the two countries, according to Reuters.

“We gave (German Chancellor Angela) Merkel 4,500 dossiers, but have not received an answer on a single one of them,” he told members of his ruling AK Party.

In Berlin, a German government source rejected Erdogan's latest remarks.

“Everything has really been said about this,” said the source.  “Repeating the same accusations over and over again does not make them any more true.”

Reuters says already tense relations deteriorated further last month after Turkey arrested 10 rights activists, including a German, as part of a wider security crackdown.

A Turkish prosecutor has reportedly accused them of links to the network of Muslim cleric Fethullah Gulen, whom Ankara blames for a failed coup in July 2016.  The U.S.-based Gulen denies any involvement.

Erdogan also revived warnings of military action against Kurdish fighters in Syria that could set back the U.S.-led battle against Islamic State (ISIS).

Kurdish fighters are spearheading an assault against the hardline militants in their Syrian stronghold Raqqa.

Media reports say that U.S. backing for the Kurdish YPG fighters in Syria has infuriated Turkey, which views their growing battlefield strength as a security threat.