In Eastern Anatolia, Istanbul Mayor and vice presidential candidate, Ekrem Imamoglu, has been pelted with rocks by Erdogan supporters.

He said nine people were injured as a result. He was campaigning in Erzurum, a stronghold of incumbent President Recep Tayyip Erdogan's AK party. While addressing his supporters from the top of an open-air bus, some members of the crowd threw stones at him.

Turkey’s opposition has long said that the country’s elections are played out on an unlevel playing field, claims often backed by international observers.

Media coverage stands out as the most obvious example of where Erdogan enjoys an advantage over his opponents, but factors such as the use of state resources while campaigning and the questionable interpretation of electoral law also feature.

Some 90 per cent of Turkey’s media is in the hands of the government or its backers, according to Reporters Without Borders, ensuring overwhelming airtime for the president. Only a handful of opposition newspapers remain in print, most having transitioned to online-only editions.

During April, Erdogan received nearly 33 hours of airtime on the main state-run TV station, according to opposition members of the broadcasting watchdog. His presidential opponent, Kemal Kilicdaroglu, received 32 minutes.

The main opposition party, the Republican People’s Party, last month launched legal action against broadcaster TRT for failing to screen its campaign video.