A group of former lawmakers on April 5 joined former envoys and retired admirals in releasing a statement to urge the government to rule out withdrawing from the Montreux Convention.
The statement titled "The core characteristics of our republic can't be discussed! Kanal Istanbul can't be constructed! Montreux can't be opened up for debate!" came two days after the retired admirals' declaration that drew backlash from the ruling Justice and Development Party (AKP).
Top government officials on April 4 accused 104 retired soldiers of suggesting a coup in their declaration, prompting prosecutors to issue detention warrants for 14 of its signatories. Ten of the retired admirals were detained on April 5 over "conspiring against state security and constitutional order."
The retired soldiers' declaration came after 126 former envoys released a statement on the issue on April 1.
The former deputies stressed in their statement that everyone has the right to state their opinions when it comes to the country's interests.
"This is both a right and a citizenship duty," the former MPs said, noting that all three groups felt that it was necessary to release these statements since President Recep Tayyip Erdoğan's "unconstitutional" withdrawal from the Istanbul Convention - an international accord designed to protect women - with a midnight decree and the Kanal Istanbul project led to discussions on the Montreux Convention.
"We find it wrong to insist on building Kanal Istanbul that will serve other states' ambitions against Turkey and to open the Montreux Convention up for debate," the former lawmakers said, referring to the construction of a massive canal connecting the Black Sea north of Istanbul to the Sea of Marmara to the south, parallel to the Bosphorus strait.
A Turkish official has said the Montreux Convention would not cover the canal.
Slamming the detention of the retired admirals and accusations directed at them, the former deputies noted that "it's unacceptable" for those who should be the guarantors of constitutional rights to try to silence and intimidate the public.
"We condemn this approach and these attempts and remind [the government] that we are still a state of law," they noted.
AKP officials on April 4 deemed the former soldiers' declaration a direct challenge to civilian government and evoked past army interventions.
Turkey's military staged three coups between 1960-1980 and pressured the first Islamist-led government out of power in 1997.
The retired military personnel had voiced concern over Montreux - which they said was strategically important for Turkey's maritime security - given Erdoğan's authority to withdraw from such pacts.
'An important treaty in terms of Turkey's survival'
Montreux, signed in 1936, gives Turkey control over the Bosphorus and Dardanelles straits within its borders, and during peacetime guarantees access for civilian vessels. It also limits access of naval warships and governs foreign cargo ships.
"Montreux provided Turkey the possibility to maintain its neutrality during World War II," said the statement by the retired military officials.
"There is a need to avoid any statements and actions that could cause the Montreux Convention, an important treaty in terms of Turkey's survival, to be brought up for discussion."
The secularist armed forces were once the dominant force in Turkey but Erdoğan and his Islamist-rooted AKP have eroded their influence since coming to power in 2002.
Presidential spokesman İbrahim Kalın said the statement had the hallmarks of a military plot to overthrow the government.
"A group of retired soldiers is putting themselves into a laughable and miserable position with their statement that echoes military coup times," he said.