ANKARA, April 22 (Reuters) - The candidate for Turkey's main opposition party has asked the Constitutional Court to order a re-run of a contested mayoral ballot in the capital Ankara, where he lost to Prime Minister Tayyip Erdogan's AK Party.
The secularist Republican People's Party (CHP) says last month's close Ankara race was marred by fraud including problems with vote counting - charges that Turkey's High Election Board has already rejected.
Nationwide local ballots saw the Islamist-rooted AK Party sweep to victory despite weeks of anti-government protests last summer and a widespread corruption scandal that has dogged Erdogan and his inner circle since late last year.
The CHP hoped to grab control of Turkey's two man cities, Istanbul and Ankara, in the vote that turned into a de-facto referendum on Erdogan's increasingly authoritarian 11-year rule.
In the event, it won neither, but CHP's unsuccessful mayoral candidate in Ankara, Mansur Yavas, tweeted late on Monday that he had taken the battle to the Constitutional Court.
"Today by using my individual right, I have appealed to the Constitutional Court. From now on, it's up to the Constitutional Court to accurately reflect the will of Ankara residents," he said.
However, it remains unclear whether the Constitutional Court has the authority to overturn the decision of the High Electoral Board. Government officials say it does not and it was not clear when the court would rule on the admissibility of the case.
On Tuesday, a CHP adviser said Yavas would take his fight to the European Court of Human Rights if necessary.
The electoral board did cancel one mayoral vote on Monday - a race in the northwestern district of Yalova, where first the AK and then the opposition were announced victors. A re-run will take place on June 1, local media reported.
Despite a history of military coups and political instability, this is the first time that a poll in Turkey has attracted such widespread allegations of irregularities.
The dispute comes amidst a wider debate over whether Erdogan is using a raft of purges and legal reforms to tighten his grip on the police and judiciary, as part of a bitter power struggle with U.S. based Islamic cleric Fethullah Gulen, whom he blames for orchestrating the corruption allegations. (Reporting by Jonny Hogg and Humeyra Pamuk; Editing by Crispian Balmer and Alison Williams)