Monbat shares fell most among blue chips, erasing 2.29% to 6.40 levs.
CCB shares lost 1.29% to 1.53 levs on Thursday, after leading blue-chip decliners with a 1.90% drop on Wednesday.
Fibank followed with a 1.26% decrease to 3.14 levs.
Six blue chips closed lower on Thursday, one gained ground, while eight ended flat.
The wider BGBX40 index, which tracks the 40 most traded shares on the Sofia bourse, decreased 0.95% to 111.75 points, while the BGTR30 index, in which companies with a free float of at least 10% have equal weight, slid 0.68% to 502.77 points.
The BGREIT index, which tracks the performance of real estate investment trusts, fell 0.66% to 126.98 points, dragged down by an 11.68% decrease in the share price of Aktive Properties REIT [BUL:5AX].
Total regulated market trading turnover more than halved to 203,000 levs on Thursday from 433,000 levs on Wednesday.
(1 euro = 1.95583 levs)