Polls open on Sunday in Turkey with Prime Minister Recep Tayyip Erdogan seeking a third term in office.
Polling stations were due to open at 7am in the east and an hour later in the west, including the capital Ankara and Istanbul.
After eight years in power, the Justice and Development Party hopes for two-thirds of the seats in parliament to make promised amendments to the constitution.
The BBC reports the main challenger is the Republican People's Party, which is fielding a large number of younger candidates.
The AKP has presided over strong economic growth and a more assertive foreign policy during its eight years in power.
It has also seen unemployment fall to 11.5% in March, from 14.4% in the same period last year.
The AKP promises an ambitious programme of new construction if elected. Projects include a canal from the Black Sea to the Aegean, a new city outside Istanbul and new bridges, airports and hospitals.
The BBC reports campaigning has been intense and at times bad-tempered with party leaders trading insults.
Mr Erdogan has promised to draw up a new constitution if re-elected, to replace the current one which was written in 1982, two years after a military coup.
If he can win a two-thirds majority in parliament, he will be able to do this without consulting the opposition or the public.
Turkey is a member of NATO and is a candidate for membership of the European Union.