Turkish authorities last month confirmed Ekrem Imamoglu of the opposition Republican People's Party, or CHP, had narrowly won election as Istanbul's mayor, defeating ruling party candidate Binali Yildirim, a former prime minister.
Yildirim said Sunday that he thought the electoral board had reviewed the case and would "make the decision from tomorrow." But Imamoglu said the elections were over and results were clear, adding that while it was a democratic right to object to the results, the ruling party was claiming fraud simply because it lost.
More than 100 people are under investigation for alleged fraud during the vote count and the entering of data in three Istanbul districts. Turkey's official Anadolu news agency reported Sunday that 41 of the people prosecutors investigated had deposited money in private Bank Asya and two allegedly used an encrypted messaging application. Turkish courts have treated both as evidence of links to cleric Fethullah Gulen, who the government accuses of being behind a failed coup.
Imamoglu's victory was a major upset for President Recep Tayyip Erdogan's Justice and Development Party. Istanbul, with its 15 million residents and strategic location straddling Europe and Asia, is Turkey's financial and cultural heart, making up about a third of the country's economy.
The ruling party also lost control of Ankara, the capital. Both Ankara and Istanbul had been held by Erdogan's conservative, religious-based party and its predecessor for 25 years. The weeks of uncertainty over election results has caused unease in financial markets, negatively affecting the national currency.