Borsa Istanbul's BIST 100 index fell 0.41 percent -- 435.59 points -- on Friday, opening at 106,389.74 points.
On the last transaction day of the week, the banking and holding sector indices decreased by 0.43 and 0.12 percent, respectively.
Among all sectors, the leasing factoring index was the best performer with a 0.30 percent rise, while the electricity index started the day with the biggest decline, falling by 1.15 percent.
The market closed at 106,825.33 points on Thursday after decreasing just 0.03 percent, while total trading volume of the BIST 100 was 5.3 billion Turkish liras (around $1.5 billion) during the day.
The U.S. dollar/Turkish lira exchange rate rose to 3.5260 at 9.30 a.m. local time (0630GMT) Friday, compared to 3.5150 at Thursday's close.