"The coup plotters stole this country's future. Any kind of coup attempt, successful or not, is treason to this country," the premier said during a related program at the ruling Justice and Development (AK) Party headquarters in the capital Ankara.
"We will not forget Feb. 28 and will not allow it to be forgotten," he added.
In February 1997, the military was involved in the collapse of late Prime Minister Necmettin Erbakan’s administration amid concerns expressed by generals about the government’s alleged Islamist program.
Erbakan was forced to sign into law the army's decisions on issues such as a ban on headscarves in public service and the shutting down of Quranic schools.
Erbakan's government was forced to step down following a National Security Council meeting. His Welfare Party was later also outlawed. A new civilian government then took over from Erbakan in a move that became known as Turkey’s 'postmodern' coup.
Yildirim said Turkey would soon complete hearing the Feb. 28 case.
"They [perpetrators] will get the heaviest penalty that they deserve within the legal framework, not based on revenge," he added.
Last December, a prosecutor recommended life sentences for two former generals over the 1997 military memorandum.
The prosecutor requested that 60 suspects, including Ismail Hakki Karadayi, then-Chief of General Staff, and Cevik Bir, his then-deputy, be produced for trial. The case includes a total of 103 suspects.
Yildirim said those people who were excluded from politics then, "are now in power and calling the coup plotters to account".