The party of Turkish President Recep Tayipp Erdogan suffered a major defeat during Sunday's local elections.
The president's Islamic-based Justice and Development Party, or AKP, lost control of Turkey's capital, Ankara, marking a significant setback to Erdogan's 16 years of power there.
AKP lost Ankara to Turkey's secular, main opposition party, the Republican People's Party, or CHP.
The CHP's mayoral candidate for Ankara, Mansur Yavas won control of Ankara after 25 years of rule by the AKP and a predecessor party.
The 63-year-old lawyer received more than 50 percent of the votes, according to state broadcaster TRT. The CHP and its allies increased the number of city mayoral seats from 14 in the previous local elections in 2014 to 20, according to the preliminary results.
"History is being written in Ankara," said deputy CHP leader Haluk Koc, while thousands of supporters celebrated the party's win in Ankara.
Voters are anxiously awaiting the ballot results for Istanbul.
Former Prime Minister Binali Yildirim, the AKP party's candidate for mayor of Istanbul declared victory even though the race is too close to call. Preliminary results showed Erdogan's opposition narrowly ahead of in Istanbul, the country's largest city.
CHP leader Kemal Kilicdaroglu disputed Yildirim's claims and rebuked AKP for declaring victory in Istanbul "in haste."
Istanbul is important to Erdogan because that's where he began his rise to power as its mayor in 1994. He has said during campaign rallies that "whoever wins Istanbul, wins Turkey."
Sunday's elections were a test for Erdogan in a nation rocked with economic turmoil. Although he wasn't on the ballot, Erdogan campaigned tirelessly for AKP's candidates. He framed the local elections as an issue of "national survival" and blamed the country's weak economy on Turkey's enemies.
Turkey's Lira continues to fall as the nation's citizens face rising inflation and unemployment – especially among young people.