Early exit polls until 2 p.m., Friday, show that Seyed Ebrahim Raeisi is leading by a narrow margin in 15 provinces against his rival Hassan Rouhani, who is leading in 12 provinces, by a wide margin, against Raeisi.
The estimated reports show that the two hopefuls hold equal votes in three provinces of Isfahan, East Azerbaijan and Zanjan.
Polls will close at 18 p.m., local time, although authorities often extend voting into the evening.
Ballot counting will start at midnight and final results are expected within 24 hours of polls closing.
LR