Turkey's benchmark index closed the day down 569.65 points on Wednesday to stand at 90,804.13 points.
The Borsa Istanbul's BIST 100 index dropped 0.62 percent. The total trading volume was 5.8 billion Turkish liras ($1.58 billion).
The U.S. dollar/Turkish lira exchange rate was down to 3.6700 liras as of 5 p.m. local time (1400GMT) Wednesday, compared with 3.6840 liras at Tuesday's close.
A dollar was exchanged for 3.6920 liras last Friday, after seeing a historic jump to 3.94 liras in mid-January.
Borsa Istanbul's gold exchange index was flat and the price of gold per kilogram was 151,070 liras ($41,164) as of 4.30 p.m. local time (1330GMT), down from 152,500 liras ($41,375) at Tuesday's close.
The banking and holding indices fell 1.37 and 0.31 percent respectively and the technology index was the best performer with an increase of 2.41 percent. Construction was the worst performing sector, falling 2.37 percent.
Stocks in Global Yatirim investment trust climbed the most, rising by 7.87 percent, while Odas Elektrik shares suffered the greatest slump, falling 2.81 percent.
The five most traded stocks were in lenders Garanti and Halkbank, Turkish Airlines, steel company Eregli and defense firm ASELSAN. -