Polling stations opened in 32 eastern Turkish provinces and 49 central ones, for the Sunday referendum on constitutional changes.
The vote in the west of the country is expected to begin at 5:00 GMT and will last until 14:00 GMT.
About 53.3 million of voters are expected to cast their ballots at 167,140 polling stations, with 461 additional stations in prisons. Turkish expats have already voted.
The amendments were approved by the Turkish parliament in January, despite the criticism from the opposition parties that see the move as a power grab attempt by President Recep Tayyip Erdogan.
The changes, if passed, would result in the elimination of the post of the prime minister, while presidential powers would be significantly expanded.
Source: Websites
