Turkish President Recep Tayyip Erdogan says there was "illegality" in Istanbul's local elections, after the country's electoral body ordered them to be re-held.
"We sincerely believe there is... organised corruption and complete illegality," he said on Tuesday.
The decision to re-run last month's vote, which returned a slim win for the opposition, sparked protests on Monday.
The opposition CHP's victorious mayoral candidate said it was "treacherous".
The European Parliament has also said the decision to re-run the election on 23 June would end the credibility of democratic elections in Turkey.
Source: National News Agency