Turkey's benchmark stock index started Thursday down 0.15 percent or 144.84 points to open at 97,043.02 points.
The banking and holding sector indexes declined 0.38 percent and 0.35 percent, respectively.
The BIST banking index was the worst performer at open, while the tourism sector index was the top gainer with a 0.61 percent increase.
On Wednesday, Borsa Istanbul's BIST 100 index fell 0.99 percent to close at 97,187.87 points with a trading volume of some 7.47 billion liras ($1.24 billion).
The U.S. dollar/Turkish lira exchange rate stood at 6.0710 as of 9.30 a.m. local time (0630GMT), compared with Wednesday's closing rate of 6.0340.
The euro/lira rate was 6.9860 on Thursday morning, versus 6.9620 at the previous close, while one British pound was traded for 7.8740 Turkish liras, versus 8.8460 at Wednesday's close.
The price of Brent oil dropped to $86.19 per barrel as of 10 a.m. local time (0700GMT) Thursday, compared to the previous close at $86.29.