ANKARA: Turkish President Recep Tayyip Erdogan on Monday accused 104 retired admirals of "hinting at a political coup" by criticising his plans for a new canal linking the Black Sea to the Mediterranean.

Turkish prosecutors detained 10 of the admirals on Monday and ordered four others to turn themselves in after they published an opened letter critical of the proposed Canal Istanbul over the weekend.

"The duty of retired admirals -- 104 of whom come together -- is not to publish declarations that hint at a political coup," Erdogan said.

"In a country whose past is filled with coups, (another) attempt by a group of retired admirals can never be accepted," he said after the former commanders criticised his plans for Canal Istanbul.

Officials last month approved a project to develop a new 45-kilometre (28-mile) shipping lane comparable to the Panama or Suez canals but it has raised questions over Turkey's commitment to the Montreux Convention.