ANKARA, March 31 (Xinhua) -- The partial results showed Turkey's ruling party, which was leading in Sunday's local elections with the slightest margin in Istanbul race, was setting to lose capital Ankara.

The People's Alliance, between ruling Justice and Development Party (AKP) and its ally the Nationalist Movement Party (MHP), was leading with 51.7 percent of the votes in local elections on Sunday after 91 percent of ballots were counted, state broadcaster TRT said.

Meanwhile, opposition Nation's Alliance, between the main opposition Republican People's Party (CHP) and the Good Party, gained 37.6 percent of the votes.

During the tight race in the largest city of Istanbul, the ruling party's candidate Binali Yildirim, the former prime minister, was taking a quite narrow lead with 48.7 percent of votes, against his opposition rival with 48.6 percent as over 98 percent of ballot boxes opened.

Yildirim declared his victory in his Istanbul headquarters late Sunday while his CHP rival Ekrem Imamoglu dismissed his statement as a "manipulation."

Shortly after Yildirim's statement, the main opposition party CHP chairman Kemal Kilicdaroglu also said his party had won in all three of the country's biggest cities - Ankara, Istanbul and Izmir.

Turkish President Recep Tayyip Erdogan said after preliminary results that his party has emerged as the winner of Turkey's mayoral elections "by a wide margin."

In the capital Ankara, Mansur Yavas, the candidate from main opposition CHP, had a narrow but firm lead of 50.6 percent in Sunday's local elections against his AKP's rival.

In Turkey's third largest city Izmir, CHP has gained the majority of votes against the ruling party as over 58 percent of the votes were counted.

Around 57 million people were eligible to participate in the municipal elections, in which voters chose for mayors, city council members and neighborhood heads.

Voter turnout was more than 83 percent, according to state-run Anadolu Agency.