ANKARA (Anadolu) — Turkish authorities arrested 10 retired admirals on Monday after a group of more than 100 retired senior naval officers issued a statement that government officials tied to the history of military coups in Turkey.

According to the state-run Anadolu news agency, the retired admirals have been detained as part of an investigation into their open letter. Four other defendants have to report to Ankara police within three days, prosecutors opting to not detain them given their age. The former senior military officials are accused of “using force and violence to get rid of the constitutional order”, NTV reported.

The detentions come a day after an open letter signed by 104 retired admirals was strongly condemned by the presidential office, which said the move was “reminiscent of coups” in Turkey’s past, Al Jazeera reported. The 14 men are accused of organising the declaration. Prosecutors opened an investigation on Sunday into the former senior naval officers on suspicion of “having conspired to commit a crime against state security and the constitutional order.”

Ankara’s approval last month of plans to develop a navigation canal in Istanbul, comparable to the Panama or Suez canals, has opened the debate on the 1936 Montreux Convention. Kanal Istanbul (“Istanbul Canal”) is the most ambitious of what President Recep Tayyip Erdogan calls his “crazy projects”, which have seen him build new airports, bridges, roads and tunnels during his 18 years in power.

In their letter published on Saturday night, the retired admirals said it was “worrying” to bring the Montreux treaty up for debate, calling it an agreement that “best protects Turkish interests”. The Montreux Convention guarantees the free passage of civilian ships through the Bosphorus and Dardanelles straits in peacetime as well as in wartime. It also regulates the use of the straits by military vessels of non-Black Sea states. The waterway linking Europe to Asia through the two straits in Turkey is congested with shipping traffic and has seen several shipping accidents in recent years.

“They (the admirals) must know that our esteemed nation and its representatives will never allow this mentality”, presidential spokesman Ibrahim Kalin tweeted. Turkey’s defence ministry said the text had “no other purpose than to undermine our democracy.”