President Tayyip Erdogan told crowds of flag-waving supporters on Sunday that Turkey could hold another referendum on reinstating the death penalty, as he claimed victory in a vote that will hand him sweeping new powers.

Addressing crowds in Istanbul, Erdogan said he would "immediately" discuss the issue of bringing back the death penalty with Prime Minister Binali Yildirim and the leader of the nationalist opposition. Such a move would spell the end of Turkey's accession talks with the European Union.

Erdogan also said votes in favour of constitutional changes to replace Turkey's parliamentary system with an executive presidency stood at 51.5 percent. He said everyone should respect the nation's decision, and added Turkey would "shift gears" in the coming period.