The rally kicked off at 3:30 p.m. (12:30 GMT), but the square was already packed with people 30 minutes before the start. Turkish flags and campaign posters for Erdogan can be seen everywhere.
Those wishing to participate in the rally have to go through a two-step security check as they are first manually checked by presumably plainclothes police officers and then walk through a metal detector flanked by special forces soldiers.
Turkiye's presidential and parliamentary elections are set to take place on May 14. The second round, which will take place if no candidate gains 50% of votes, is scheduled for May 28.