"The nation has entrusted to me the responsibility of the presidency and the executive duty", 64-year-old Mr Erdogan said.
In the parliamentary contest, the AK Party had 43 percent and its MHP ally almost 11 percent, based on 90 percent of votes counted, broadcasters said. "Turkey will reach their level of development too and will be among the top ten countries in this respect", Erdogan said. Incumbent President Recep Tayyip Erdogan is facing a tough challenge from his main rival, Muharrem Inje. There will be less bureaucracy and more investments.
Earlier in the day, officers have arrested 10 foreigners of France, German and Italian descent who have been accused of posing as some of Turkey's eye-watering one million ballot box monitors shipped in to stamp out voter tampering.
Voters are flocking to polling centres today to cast ballots in an election that will complete Turkey's transition to a new executive presidential system, a move approved in a controversial referendum a year ago.
The main opposition party did not immediately concede defeat. "I hope nobody will damage democracy by casting a shadow on this election and its results to hide their failure".
Election observers and party members should not "abandon the ballot boxes", he said.
Turnout exceeded a massive 87 percent.
The polls - for which more than 55 million Turkish voters are registered - will also finalize Turkey's transition to an executive presidency, which was narrowly approved in a contentious election a year ago.
At his own rally, President Erdogan - who was prime minister for 11 years before becoming president in 2014 - used a violent metaphor to summarise his hoped-for result, asking supporters, "Are we going to give them an Ottoman slap [a technique for knocking someone out] tomorrow?" The president will also be able to dissolve parliament, issue executive decrees, and impose a state of emergency.
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The parliamentary election results so far are similar, with a substantial lead for the ruling AK Party.
Erdogan needs over 50 percent to retain the presidency in the first round but these are still early results and the outcome could yet change drastically.
The stakes in this election are particularly high as the new president is the first to enjoy enhanced powers under a new constitution agreed in an April 2017 referendum strongly backed by Erdogan.
The votes of Turkey's Kurdish minority will be especially crucial in the parliamentary poll.
Opposition parties, on the other hand, did not win enough seats to stop a bill from being enacted into law in parliament. Up to 300 people chanted "Thief Tayyip!" inside the CHP party headquarters in Ankara.
The AK Party, which has been in power since 2002, received approximately 42.5 percent of the votes to win its sixth consecutive general election. "That 10 percent apparently came from his ally, MHP", Mustafa Akyol, a Turkish columnist and analyst, told Al Jazeera.
That has been the case since the AK Party aligned with the once-opposition MHP in late 2015. "It gives it a lot of power".
With 99 percent of votes counted in the presidential race, Erdogan had 52.5 percent, well ahead of Ince's 31 percent, broadcasters said. A state of emergency has been in place since the coup.
Turkey held Sunday's elections under a state of emergency declared after a failed military coup in July 2016 that Erdogan blamed on his former ally, US -based Muslim cleric Fethullah Gulen.
Turkey's Western allies have repeatedly condemned the Turkish government's detentions and purges after the coup attempt.