While the board, known as YSK, had not yet made a statement, the decision was announced by state-run Anadolu agency and a representative of the ruling AK Party (AKP), Recep Ozel, who said a second vote would take place on June 23.

Turkey’s main opposition Republican People’s Party (CHP), which in the initial vote on March 31 narrowly won the mayoralty in the country’s largest city, called the ruling a “plain dictatorship.”

The AKP had appealed for an election re-run after initial results and a series of recounts showed it had lost control of Istanbul for the first time in 25 years.

It was a shock loss for Erdogan who in the 1990s served as the city’s mayor and had campaigned hard ahead of the nationwide local vote, his first electoral test since last year’s sharp currency crisis tipped the Turkish economy into recession.

The Turkish lira weakened after Ozel, the AKP’s representative on the YSK, tweeted the decision, and it was at 6.1075 against the dollar at 1730 GMT and on track for its worst day in more than a month.

The lira has tumbled some 10 percent since a week before the initial election. Suspense over the ruling had left investors worried that weeks of additional campaigning would divert funds and attention from addressing economic reforms.

It was unclear how the CHP and its supporters would respond to a re-run given suspicions over the YSK’s political independence from the AKP, which in recent years has centralized power in the presidency away from the central bank, courts and other institutions.

“It is illegal to win against the AK Party,” CHP Deputy Chairman Onursal Adiguzel said on Twitter. “This system that overrules the will of the people and disregards the law is neither democratic, nor legitimate. This is plain dictatorship.”

The AKP also lost the mayor’s office in the capital Ankara. With its nationalist MHP allies, it wanted the Istanbul results annulled and cited irregularities that affected the outcome, which put it some 13,000 votes behind CHP.

On Saturday Erdogan said “it’s clear” the vote was marred by controversy and urged the YSK to “clear its name” with a re-run.

Istanbul’s new CHP mayor, Ekrem Imamoglu, officially took office last month after a smattering of partial and full recounts were completed across the city. Since then, prosecutors launched probes into the alleged irregularities and called 100 polling station workers in for questioning as suspects.

Reporter’s code: 50101