Turkey detected a third floating naval mine in its waters in the Black Sea and military diving teams were working on defusing it, the defence ministry said on Wednesday amid the invasion of Ukraine.
NATO member Turkey borders the Black Sea, as do Russia and Ukraine, which Moscow invaded on February 24.
The Black Sea is key for shipping grain, oil and oil products.
Its waters are shared by Bulgaria, Romania, Georgia and Turkey, as well as Ukraine and Russia, which have been at war since President Vladimir Putin's troops invaded his southern neighbour.
Ukraine and Russia have accused each other of laying mines in the Black Sea, and in late March, Turkish and Romanian military diving teams defused stray mines around their waters.
Maritime officials say the risk of coming across floating mines in the major Black Sea shipping route is adding to perils for merchant ships sailing in the region, and governments must ensure safe passage to keep supply chains running.