Speaking to reporters on board his airplane after a visit to the southeastern province of Diyarbakir over the weekend, Erdogan accused Moscow of transferring weaponry to the PKK via Iraq and Syria, Reuters quoted Star newspaper.
"At this moment, terrorists are using anti-aircraft guns and missiles supplied by Russia. The separatist terrorist organization is equipped with these weapons. They have been transferred to them via Syria and Iraq," the Star reported Erdogan as saying.
The government was not immediately available to confirm the report.
Erdogan comments appear to be the first time he has accused Moscow of supplying arms to the PKK, seen as a terrorist group by Turkey, the United States and Europe, Reuters said.
Ankara also considers the Syrian Kurdish YPG fighters to be a terrorist group and has been enraged by both Russian and U.S. backing for the group, which is battling Islamic State militants in Syria.
Relations between Ankara and Moscow soured after Turkey shot down a Russian warplane over Syria last year, prompting a raft of sanctions from Russia.
Russian President Vladimir Putin in April promised support for Syrian Kurds, saying they were a serious force in the fight against terrorism.
Russia has also accused Turkey of hindering Kurdish forces in their fight against Islamic State and using the fight against terrorism as a pretext to crack down on Kurdish organizations in Syria and Turkey.