Turkey's Prime Minister Binali Yıldırım has performed the first weld at a keel-laying ceremony at the Gölcük shipyard for the Turkish Navy's third Reis-class (Type 214) submarine.
The submarine will carry the name of Murat Reis, an Ottoman Navy admiral.
Turkey is constructing a fleet of six new Type 214 air-independent propulsion submarines under a €2.5 billion (US$3.0 billion) contract signed with German ThyssenKrupp Marine Systems in 2009.
Construction on the first vessel, TCG Piri Reis, started in 2015.
Type 214 submarines are 65 metres long and reach speeds of 20 knots while submerged.
The first submarine in the class is expected to be delivered in 2021.