Turkey's benchmark stock index fell 0.26 percent or 309.04 points to open at 117,323.03 points on Friday.
The banking and holding sector indices lost 0.33 percent and 0.36 percent, respectively.
Among all sector indices, the investment trusts sector index was the best performer, gaining 0.51 percent, while the basic metal industry sector index saw the biggest fall, losing 0.75 percent.
The U.S. dollar/Turkish lira exchange rate went down to 3.8070 as of 9.30 a.m. local time (0630GMT), compared to Thursday's closing rate of 3.8140.
The euro/lira rate rose to 4.6740 on Friday morning, compared to 4.6500 at the previous day's close.
The price of Brent oil was $63.83 per barrel as of 09.52 a.m. local time (0652GMT) Friday, versus $63.46 at close on Thursday.