Table-topping Pohang Steelers continued their excellent season with a 1-0 win over Seoul at the Steelyard Stadium on Wednesday.
The away side were looking to avoid back-to-back defeats and appeared to be on their way to a hard-earned point before Mu-Yeol Ko's 88th-minute strike.
It was an important goal for Pohang and a sign that they were back on track following Saturday's 2-1 loss to Incheon United.
Ulsan maintained the pressure at the top of the table as they staged a come-from-behind 3-1 victory over Chunnam Dragons.
Robert Cornthwaite fired the away side into a 51st-minute lead after a first half that featured few clear-cut chances.
Their advantage was short-lived, however, as just eight minutes later Sang-Woon Han restored parity.
And Ulsan took the lead in the 67th minute via a Rafinha strike before the Brazilian grabbed his second of the game in second-half injury time.
The result ensured they stayed within two points of the leaders.
Struggling Daejeon Citizen's woes continued as they lost their sixth game in seven matches by going down 3-1 away to Suwon Bluewings, extending their winless run to 12.
Hong Chul opened the scoring in the 25th minute at the Suwon World Cup Stadium and by the 32nd minute they were 3-0 ahead through further efforts from Macedonian Stevica Ristic and Jung-Jin Seo, who grabbed his fifth goal of the season.
Daejeon showed some fighting spirit in the second half courtesy of Joao Paulo's 72nd-minute strike but the result was already beyond doubt, as Suwon moved up to fourth.
Daegu secured a precious three points with a 3-2 success over Gyeongnam at the Daegu Main Stadium.
Il-Soo Hwang got the home side off to the perfect start in the sixth minute, but they were pegged back in the 15th via Milan Bubalo.
But the real drama unfolded in the last 15 minutes of the second half, with three goals in a thrilling climax.
Derek Asamoah put Daegu ahead from the penalty spot in the 76th minute but with three minutes remaining Bubalo's spot-kick looked to have rescued a point for the away side.
However, Soon-Min Hwang's finish in the last minute of normal time wrapped up a dramatic finish.
Elsewhere, Jeonbuk Motors lost out by the odd goal in five at home to Seongnam with the game decided by a controversial incident.
With Seongnam leading 2-1, Jeonbuk accidentally scored when attempting to return the ball after a break for an injury.
Angry scenes ensued after the goal before Eun-Seong Choi sportingly scored an own goal to ensure a 3-2 triumph for Seongnam at the Jeonju World Cup Stadium.
Gangwon and Busan I'Park played out a 2-2 draw.