South Korea's ruling Saenuri Party suffered a narrow defeat but overall performed better than expected in Wednesday's local elections.
The polls were seen as a key test for President Park Geun-hye, whose popularity rating has sunk following the deadly Sewol ferry accident.
Park's Saenuri Party took eight of 17 key mayoral and provincial races. The main opposition New Politics Alliance for Democracy took nine.
A presidential spokesman on Thursday said Park "humbly" accepts the election results and will do her best "to rebuild the country."
Park has repeatedly apologized for the April 16 sinking of the Sewol, which killed 300 people, mostly high school students.
Many South Koreans are upset at what they see as lax safety standards that led to the disaster, as well as an inadequate rescue attempt.