Turkish President Recep Tayyip Erdogan said Saturday there will be no mercy for traitors.
Speaking at a rally in Istanbul to mark one year of a failed coup, Erdogan warned to "chop off the heads" of traitors.
The opposition says his call for "chopping off the heads" may return the capital punishment abolished in August 2002, in a bid to join the European Union.
Erdogan said that he would approve "without any hesitation" any legislation that would reinstate capital punishment in Turkey.
"I spoke to the prime minister and [...] when they appear in court, let's make them appear in uniform suits like in Guantanamo," Erdogan added. "Nobody who betrays this nation can remain unpunished."
On his part, Prime Minister Binali Yildirim called the coup attempt a dark moment for Turkey, with deadly clashes between the people and rogue military forces. "It has been exactly one year since Turkey's darkest and longest night was transformed into a bright day, since an enemy occupation turned into the people's legend," he said.
"Our people did not leave sovereignty to their enemies and took hold of democracy to the death," he went on, as Erdogan and members of opposition parties looked on. "These monsters will surely receive the heaviest punishment they can within the law."
Beyond the groundswell of nationalism, the coup's greatest legacy has been the far-reaching purge on multiple sectors of Turkish society.
About 150,000 people have been sacked or suspended from jobs in the civil service and private sector. More than 50,000 have been detained for alleged links to the putsch.
A fresh wave of firings came on Friday, when the government announced it had dismissed another 7,000 police, civil servants and academics for suspected links to the US-based Muslim cleric Fatullah Gulen it blames for the putsch.
Western governments and human rights groups have repeatedly criticized the purge which has taken place following the coup as well as the conduct of the referendum voting.
President Erdogan and his supporters have spoken of "foreign hands" behind the coup plot. Western governments, they charge, had been slow in condemning the coup against a democratically elected government, waiting to see which side won.
Interestingly, hundreds of thousands gathered at a protest rally in Istanbul last Sunday, July 9. Kemal Kilicdaroglu, the leader of the opposition Republican People's Party (CHP), who had headed a 25-day, 425 km (265 mile) "justice march" from Ankara to Istanbul, to protest the detention of a CHP lawmaker. He declared it was a "rebirth for us, for our country and our children".
Critics, including rights groups and some Western governments, say that Erdogan is using the state of emergency introduced after the coup to target opposition figures including rights activists, pro-Kurdish politicians and journalists.
The pro-Kurdish Peoples' Democratic Party (HDP) was represented by its deputy chairman as the party's two co-leaders are in jail - as are local members of rights group Amnesty International and nearly 160 journalists, according to the Committee to Protect Journalists.