K-League leaders Seoul battled to a 1-1 draw with second-placed Jeonbuk Motors on Saturday to maintain their seven-point gap.
The visitors will be happy with a point against their nearest rivals despite taking an early lead through Dong-Woo Kim.
Dong-Gook Lee answered just before the hour mark for Jeonbuk but the home side desperately needed the win to maintain their title challenge with seven games in the championship round remaining.
Sixth-placed Jeju United went ahead through Brazilian Renan's penalty on seven minutes before he equalised for Busan I'Park on the stroke of half time with an own goal.
Substitute Dong-Hyeon Seo was on hand in stoppage time to take all three points for Jeju in a 2-1 win.
In the relegation round, top side Incheon United defeated Gwangju 3-2 after trailing in the first half.
Gyo-Won Han and Ki-Hyeon Seol netted for the hosts to extend their unbeaten run to 13 games.
The other fixture between rock-bottom Sanju Sangmu and Gangwon was cancelled as the relegated side continues to boycott the remainder of the season.