Turkish President Recep Tayyip Erdogan was returned to office with expanded powers, the country's electoral board said Sunday, brushing aside opposition claims that the results were incomplete.

Sadi Guven, the head of the Supreme Election Council, said that 97.7 percent of votes in the presidential race had been counted and Erdogan had received an "absolute majority."

Unofficial results from the state-run Anadolu Agency showed Erdogan with 52.5 percent of the vote and his main rival Muharrem Ince at 30.7 percent. Kurdish candidate Selahattin Demirtas, who ran his campaign from jail while awaiting trial on terrorism-related charges, was garnering 8.4 percent. Former Interior Minister Meral Aksener, who broke away from Turkey's main nationalist party over its support for Erdogan, received 7.3 percent of the vote.

However, Ince had claimed the results carried on Anadolu were not a true reflection of the official vote count. In a tweet earlier in the evening, he said only 37 percent of ballot boxes had actually been counted, as opposed to the more than nearly 90 percent Anadolu was reporting at the time. He accused the agency of "manipulation" of the results.

"This election's victor is democracy, this election's victory is national will," Erdogan told a cheering crowd outside his party headquarters in Ankara early Monday, adding that Turkey "will look at its future with so much more trust than it did this morning."

Earlier, cheering Erdogan supporters waving Turkish flags gathered outside the president's official residence in Istanbul, chanting, "Here's the president, here's the commander."

"Justice has been served!" said Cihan Yigici, an Erdogan supporter in the crowd.

Sunday's simultaneous presidential and parliamentary elections took place more than a year early. They were the last step needed to complete Turkey's transition from a parliamentary system of government to a strong presidential system, a change voters approved last year.

In addition to his personal election triumph, Erdogan also claimed victory in the parliamentary vote for the People's Alliance, an electoral coalition between his ruling Justice and Development Party and the small Nationalist Movement Party.

Unofficial parliamentary results showed the People's Alliance stood at 53.6 percent and was projected to win a combined 343 seats in the new 600-member legislature. The Justice and Development Party was projected to win 293 seats, just shy of the 301 needed to hold a majority.

"Even though we could not reach our goal in parliament, God willing we will be working to solve that with all our efforts in the People's Alliance," Erdogan said.

The opposition Nation Alliance -- grouping together nationalists, secularists and a small Islamic-leaning party -- was at 34 percent and projected to win 190 seats.

Thousands of jubilant supporters of the pro-Kurdish Peoples' Democratic Party, or HDP, also spilled into the streets of the predominantly Kurdish southeastern city of Diyarbakir after unofficial results from Anadolu showed the party surpassing the 10 percent threshold needed to enter parliament and garnering 11.6 percent of the vote. HDP is projected to have 67 seats in the new parliament.

The HDP's performance was a particular success since in addition to Demirtas, eight more of its lawmakers and thousands of party members campaigned from jails and prisons. HDP says more than 350 of its election workers have been detained since April 28.

Revelers waved HDP flags and blared car horns. One party supporter, Nejdet Erke, said he had been "waiting for this emotion" since morning.

Guven, the head of the election council, confirmed that a fifth political party, the center-right Good Party, had managed to reach the required 10 percent threshold to enter parliament. Anadolu's results projected the party to hold 44 seats.

Erdogan insisted the expanded powers of the Turkish presidency will bring prosperity and stability to the country, especially after a failed military coup attempt in 2016. A state of emergency imposed after the coup remains in place.

Some 50,000 people have been arrested and 110,000 civil servants have been fired under the emergency, which opposition lawmakers say Erdogan has used to stifle dissent.

The new system of government abolished the office of prime minister and empowers the president to take over an executive branch and form the government. He will appoint ministers, vice presidents and high-level bureaucrats, issue decrees, prepare the budget and decide on security policies.

The Turkish Parliament will legislate and have the right to ratify or reject the budget. With Erdogan remaining at the helm of his party, a loyal parliamentary majority could reduce checks and balances on his power unless the opposition can wield an effective challenge.

The president's critics have warned that Erdogan's re-election would cement his already firm grip on power and embolden a leader they accuse of showing increasingly autocratic tendencies.

Erdogan's apparent win comes at a critical time for Turkey. He recently has led a high-stakes foreign affairs gamble, cozying up to Russian President Vladimir Putin with pledges to install a Russian missile defense system in the NATO-member country.

Erdogan, who has never lost an election and has been in power since 2003, initially as prime minister, had faced a more robust, united opposition than ever before. Opposition candidates had vowed to return Turkey to a parliamentary democracy with strong checks and balances and have decried what they call Erdogan's "one-man rule."

A combative president, Erdogan enjoys considerable support in the conservative and pious heartland, having empowered previously disenfranchised groups. From a modest background himself, he presided over an infrastructure boom that modernized Turkey and lifted many out of poverty while also raising Islam's profile, for instance by lifting a ban on Islamic headscarves in schools and public offices.

But critics say he has become increasingly autocratic and intolerant of dissent. The election campaign was heavily skewed in his favor, with opposition candidates struggling to get their speeches aired on television in a country where Erdogan directly or indirectly controls most of the media.

Ince, a 54-year-old former physics teacher, was backed by the center-left opposition Republican People's Party, or CHP. He wooed crowds with an unexpectedly engaging campaign, drawing massive numbers at his rallies in Turkey's three main cities of Istanbul, Ankara and Izmir.

More than 59 million Turkish citizens, including 3 million expatriates, were eligible to vote.

The Associated Press contributed to this report.