The main index of Tehran Stock Exchange, TEDPIX, lost 0.67% to end Monday’s session at 1,481,924.14.
The downturn hit smaller shares harder as seen in the 1.23% drop in equal-weighted index, which tracks all shares irrespective of size.
Observers see Monday’s sell-off as a market response to the benchmark drawing close to the psychological 1.5 million point level.
TEDPIX had stopped near the resistance level a session earlier, as investors rushed to sell shares to save earlier gains.
About 12.27 billion shares valued at 157.18 trillion rials ($818.68 million) changed hands at TSE for the day.
Bahman Group Company was the biggest winner as its shares climbed 11.98% to 16,730 rials per share.
Mobin Energy Persian Gulf Company incurred the biggest loss among all TSE-listed companies and went down 5.58% to 30,640 rials per share.
Mobarakeh Steel Company contributed the most to the benchmark's fall, followed by Golgohar Mining and Industrial Company, Omid Investment Management Group Company and National Iranian Copper Industries Company.
Social Security Investment Company gave the biggest boost to the benchmark index, followed by Esfahan Oil Refining Company, Parsian Oil and Gas Development Company and MAPNA Group.
The First Market Index went down 9,577.07 points, or 0.85% to post 1,116,209.81.
The Second Market Index was down 11,041.22 points, or 0.38% to reach 2,863,527.82.
The Industry Index lost 6,892.29 points or 0.53% to register 1,303,677.44. The Free Float Index was down 20,993.16 points to hit 1,958,933.61.
TSE 30 went down 690.16 points to settle at 71,691.48 and the TSE 50 ended 310.96 points lower to finish at 57,531.17.
IFX Down 0.69%
Iran Fara Bourse main index IFX lost 110.07 points or 0.69% to close Monday trade at 15,953.44.
About 2.71 billion securities valued at 55.25 trillion rials ($287.77 million) were traded at the over-the-counter exchange for the day.
Esfahan Steel Company had the highest number of traded shares as 340.66 million of its shares worth 2.83 trillion rials ($14.78 million) were traded.
Middle East Mines and Mineral Industries Development Holding Company, Esfahan Steel Company, Zagros Petrochemical Company and Saba Tamin Investment Company had the most negative impact on IFX.
Gohar Zamin Iron Ore Company gave the biggest boost to IFX, followed by Day Bank, Marun Petrochemical Company and Jahrom Power Plant Development Company.