President Recept Tayyip Erdogan on Friday defended Russia's Vladimir Putin from allegations of meddling in Turkey's crucial weekend election.
Erdogan's secular rival Kemal Kilicdaroglu on Thursday accused unnamed Russian actors of spreading "deep fakes" and other disinformation aimed at swaying the outcome of Sunday's vote.
The Kremlin "strongly" denied the allegation and Erdogan stood up for Putin at a televised campaign appearance on Friday.
"Mr. Kemal is attacking Russia, Mr. Putin. If you attack Putin, I will not be okay with that," Erdogan said.
"Our relations with Russia are no less important than those with the United States."
Erdogan has maintained good working relations with Putin throughout Russia's invasion of Ukraine.
Turkey has benefited from rebates on Russian energy imports and refused to subscribe to Western sanctions on the Kremlin.
Polls show Erdogan locked in a tight battle against his secular opposition rival.
Kilicdaroglu's comments came in the heat of an increasingly dirty campaign that saw third-party candidate Muharrem Ince pull out on Thursday.
Ince announced his decision after being targeted by an online campaign that included doctored images of him meeting women and riding around in fancy cars.
Erdogan has also been broadcasting misleading videos during rallies that try to link Kilicdaroglu with members of a banned Kurdish militia that Turkey and its allies view as "terrorists".