March 9 (UPI) -- Istanbul's mayor, a political opponent to Turkish President Recep Tayyip Erdoğan, is among 400 current and former city employees on trial in Monday in over allegations of corruption and organized crime. Istanbul's mayor Ekrem İmamoğlu, 55, was arrested last year after announcing he planned to run for president . He is being held in a high-security prison in Istanbul. The mass trial has drawn criticism for being politically motivated. Imamoglu has been viewed as a political