Turkish President Recep Tayyip Erdogan has accused Russia of providing antiaircraft weaponry and rockets to militants of the banned Kurdistan Workers Party (PKK).
Russia has transferred the weaponry to the PKK via Iraq and Syria, Turkish pro-government media quoted Erdogan on May 30 as saying.
Turkish government officials confirmed the president's comments.
Responding to the accusation, Russian Deputy Foreign Minister Mikhail Bogdanov said, "When someone says something, let them show evidence."
Erdogan has previously criticized Moscow for its support of Kurdish fighters in Syria.
Relations between the two countries soured after Turkey shot down a Russian warplane in November 2015.
Following the incident along the Turkish-Syrian border, Russian President Vladimir Putin imposed sanctions on Turkey and trade between the two countries plummeted.
Based on reporting by Reuters, dpa, and Interfax