STORY: Erdogan cast his vote at a polling station in Istanbul as he faced the biggest challenge of his two-decade rule.

The 69-year-old leader has defied forecasts of his political demise, rallying voters with a potent mix of religious conservatism and nationalism that looks set to propel his rule into a third decade.

Meanwhile, leader of the opposition Kemal Kilicdaroglu cast his vote in Ankara. Kilicdaroglu, who received the endorsement of a far-right leader, is backed by a six-party alliance including his Republican People's Party (CHP).

The election will decide not only who leads Turkey but also where its economy is headed, and the shape of its foreign policy.