The BIST 100 index lost 319.67 points to open at 76,386.39 on Monday morning during its first transactions.
The benchmark index decreased by 0.41 percent on the third trading day of the week. The banking and holding sector indices declined by 0.51 percent.
Among all the sector indices, the wood paper printing sector index increased the most, by 0.12 percent. The textile and leather sector index saw the biggest drop, 0.71 percent, in initial transactions.
The U.S. dollar/Turkish lira exchange rate increased to 3.6730 at 9.30 a.m. local time (0630 GMT) on Monday, compared with 3.6340 at Friday's close.
It had fallen to a historic low of 3.6900 against the dollar in early trading on Monday after starting the day at 3.6510.
The fall came after U.S. labor data showed growth in the world's largest economy was poised to accelerate.
