ANKARA, March 31 (Xinhua) -- Turkey's ruling party was leading with the slightest margin to retain the country's largest city Istanbul while setting to lose capital Ankara to the opposition in Sunday's municipal elections, according to unofficial results.

Binali Yildirim, former prime minister from the Justice and Development Party (AKP), was leading a super tight race with 48.71 percent of the vote as more than 98 percent of ballot boxes opened. The main opposition Republican People's Party (CHP) candidate gathered 48.65 percent of the vote, according to media reports.

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

In Ankara, the CHP's candidate Mansur Yavas had a narrow but firm lead with 50.6 percent of the vote against 47.2 percent for his AKP rival, and was in track to end the AKP's longtime control of the capital.

Against an alliance led by the AKP, opposition parties have also come together in a rare unity in Turkey, making these elections a rivalry of political alliances.

In a first statement after the elections, Erdogan told reporters in Istanbul that the focus will be on the economy.

"There is a very strong economic plan ahead," and his government will implement strong economic plans, he was quoted by state broadcaster TRT as saying.

Generally local elections are not considered as crucially important in Turkey because voters only choose their local councilors and mayors, but this time it has been perceived as a confidential vote for Erdogan as the country's sharp economic woes bite into his popularity.

During Erdogan's 16 years in office, Turkey has seen a consistently strong economic growth, especially for lower sections of the population but last year's currency crisis has triggered a recession. The Turkish currency has plunged by more than a third of its value.

Soaring inflation and unemployment have seriously reduced consumers purchasing power and have initiated a mood of disenchantment towards the AKP, according to surveys published ahead of the elections.

Some big cities controlled by the AKP, such as Antalya in the south and Adana in the southeast, have thus been won by the CHP, according to unofficial results.

As a partial result of the elections, the ruling Party took the lead in 16 metropolitan municipalities and 24 other provinces. CHP took the lead in 10 metropolitan municipalities and 10 other provinces.