Turkey's armed forces have never used chemical weapons and they abide by international law, according to President Recep Tayyip Erdogan.
The Turkish leader said that legal action would be taken against those who have made allegations on the issue, broadcaster NTV reported on Friday.
"Our armed forces have not resorted to using chemical weapons to this day," NTV reported Mr Erdogan saying on his plane returning from a trip to Azerbaijan.
"They will always cast such slanders. We will call them to account as is required within the law."
The defence ministry and top officials on Thursday also denied that the armed forces had used chemical weapons in their operations against Kurdish militants.
Turkish prosecutors on Thursday opened an investigation into the head of the Turkish Medical Association, Sebnem Korur Fincanci, after she said on television that footage indicated the use of toxic gases and called for an independent investigation.
State-owned Anadolu news agency said Dr Fincanci was accused of "making terrorist group propaganda" and "denigrating the Turkish nation, the Republic of Turkey and its institutions".
An international medical federation published a report this month seeking an independent investigation of possible breaches of the 1997 Chemical Weapons Convention by the Turkish military.
The PKK is designated as a terrorist group by Turkey, the European Union and United States. More than 40,000 people have been killed in the fall-out from the insurgency that it launched against the Turkish state in 1984.