Turkish President Tayyip Erdogan won sweeping new executive powers after his victory in landmark elections that saw his Islamist-rooted AK Party and its nationalist allies secure a majority in parliament.
Speaking early Monday, Supreme Election Council head Sadi Guven said 97.7 percent of votes had been counted and declared Erdogan the victor.
Spokesman Bulent Tezcan of the Republican People's Party criticised Turkey's state-run news agency for reporting that Mr Erdogan has won enough to avoid a run-off and accused the agency of distorting the results.
Though his main opponent-Muharrem Ince of the secularist Republican People's Party (CHP)-has yet to officially concede, it appears Erdogan will now assume the significantly expanded powers he narrowly secured in a referendum a year ago. "I accept the results of the elections".
There are ongoing debates about whether the election was "free", amid reports of ballot stuffing and vote rigging.
Turkish voters re-elected Erdoğan to another term in office on Sunday in elections whose outcome is likely to shape the country for years or even decades to come.
Opposition leader Muharrem Ince conceded defeat, and warned that Turkey would suffer from "one-man rule" at the hands of Erdogan. More than 50,000 people have been imprisoned pending trial since the uprising.
In a series of Twitter postings, Demirtas praised the party's success in winning a projected 67 seats out of 600, according to unofficial results.
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"The restrictions we have seen on fundamental freedoms (due to the state of emergency) have had an impact on these elections", Ignacio Sanchez Amor, head of the OSCE observer mission, told a news conference. But after initially saying Erdogan would fall well short of a first-round victory, it said it would continue its democratic struggle "whatever the result".
Their members faced security problems and the mission had difficulties mostly in Diyarbakır, Ankara and Istanbul, the delegation said, criticizing the government for preventing two of their members from performing their observation mission in Turkey.
Last year, Erdogan narrowly won a referendum to convert the country's parliamentary system to a powerful executive presidency. They will continue to "liberate Syrian lands", he said, so that the 3.5 million refugees now living in the country can one day go home.
"We always vote for our leader Recep Tayyip Erdogan", he said while navigating his cab through traffic.
The amendments will transform the country from a parliamentary democracy into a presidential system - arguably the most significant political development since the Turkish republic was declared in 1923.
"Turkey is staging a democratic revolution", he told reporters after casting his own vote in Istanbul.
Erdogan has declared himself an "enemy of interest rates", raising fears he will pressure the central bank to cut borrowing costs after the election despite double-digit inflation.
Several world leaders supportive of Erdogan, including Azerbaijani President Ilham Aliyev and Qatari Emir Tamim bin Hamad Al-Thani, called to congratulate him on his "victory", the presidency said.
Turkey has been under emergency rule - which restricts some freedoms and allows the government to bypass parliament with decrees - for almost two years since an attempted coup in 2016. "The presidential election is certainly going to a second round".
Luxembourg's foreign minister said Mr Erdogan is now "all-powerful" and it will be up to him whether Turkey's relations with the European Union improve.