The Bulgarian Socialist Party (BSP) had 13.7 percent, while liberal, Western-leaning grouping Democratic Bulgaria had 12.6 percent.
The mostly ethnic Turkish-backed Movement for Rights and Freedoms (DPS) had 10.6 percent, while Stand Up! Get Out! -- a new, center-left alliance launched by former Ombudsman Maya Manolova -- was at 5 percent.
A pre-election survey by Gallup International showed ITN at 23.2 percent, ahead of GERB at 23 percent. Other polls forecast similar close results.
Popular TV host Slavi Trifonov leads the There Is Such A People party in Bulgaria.
About 6.7 million people were eligible to vote for members of the 240-seat parliament. Early estimates following exit polls gave ITN 64 seats, with GERM at 61.