Tehran Stock Exchange's all-share index plummeted 1.19% or 878.60 points to close Sunday trade at 73,027.9, its lowest since February 2.
Huge losses by large-cap telecoms, oil and gas companies, auto manufacturers and banks weighed most on TEDPIX.
The benchmark has been on a losing streak over the past few days. It shed a full 2,000 points to finish last week 2.6% lower at 73,877 points.
Close to 940 million shares valued at $69 million were transacted for the day.
Iran Telecommunications Company registered the biggest loss among all companies listed on TSE, as its shares' value sank 6.69% to 2,050 rials. It was followed by Indamin Saipa Shock Absorber Company and Behnoush Iran Company.
Toosgostar Urban Development Company posted the biggest gain, going up 4.99% to 2,084 rials per share. Goltash Company and National Iranian Lead and Zinc Company came next.
Iran Telecommunications Company was the main laggard for the benchmark, followed by Tamin Oil, Gas and Petrochemical Investment Company and Bandar Abbas Oil Refining Company.
National Iranian Copper Industries Company gave the biggest boost to TEDPIX followed by Fajr Petrochemical Company and Mobarakeh Steel Company.
The auto manufacturing sector posted the highest number of traded shares and highest daily trade value.
The Price Index lost 320 points or 1.19% to stop at 26,594.7.
The First Market Index shed 669.40 points or 1.31% to settle at 50,610.
The Second Market Index gave up 1,595.80 points or 0.97% to reach 162,606.2.
The Industry Index wiped 763.40 points or 1.24% to post 60,854.1.
The Free Float Index was down 918.57 points or 1.12% to finish at 81,118.60.
The TSE 30 Index withdrew by 33.80 points or 1.13% to record 2,951.3, while the TSE 50 Index lost 39.30 points or 1.34% to end at 2,896.3.
> IFX Down 1.11%
Iran Fara Bourse's main index wiped 8.57 points or 1.11% to close at 765.37.
The over-the-counter exchange's decline in recent days has been more than TSE's. Benchmark IFX lost 3.8% and dropped to its lowest since April 19 to finish last week at 777.06 points.
Over 454 million securities valued at $45.3 million changed hands in 36,000 transactions on Sunday.
Middle East Mines and Minerals Development Holding Company, Tehran Oil Refining Company and Hormozgan Steel Company weighed most on IFX.
More than 132 million securities valued at $4.9 million were traded in the First Market. The Second Market saw the trading of 58 million securities worth $4.5 million.
Goharan Omid Company registered the highest number of traded shares and daily trade value, as 100 million of its shares worth $3 million changed hands.
Goharan Omid Company, Fanava Company and Tabas Coal Company posted the biggest gains in share value.
Novin Insurance, Pardis Housing Investment Company and Saman Insurance experienced the biggest decline.
Bank Day, Tehran Oil Refining Company and Tehran Housing Investment Company were also on investors' radar.
Etemad Fund, with the transaction of 770,000 of its shares, posted the highest trade volume among listed exchange-traded funds. Moreover, 200,000 participation bonds of Narenjestan Complex were sold out.
