Turks began voting on Sunday in a presidential runoff that could see Tayyip Erdogan extend his rule into a third decade and persist with Turkey's increasingly authoritarian path, muscular foreign policy and unorthodox economic governance.

Erdogan, 69, defied opinion polls and came out comfortably ahead with an almost five-point lead over his rival Kemal Kilicdaroglu in the first round on May 14. But he fell just short of the 50% needed to avoid a runoff.

Voting began at 8 a.m. (0500 GMT) and will finish at 5 p.m. (1400 GMT). The outcome was expected to start becoming clear by early evening.