Seoul: Ulsan Hyundai Horang-i defeated Jeonbuk Hyundai Motors 3-2 in an Asian Champions League quarter-final on Sunday to stay on course for a second successive continental title.
Ulsan, who also won in 2012, needed extra time to beat their Korean rivals.
Knockout ties in the tournament have been reduced to a single game from the usual two-legged encounters due to the pandemic.
Georgian midfielder Valeri Qazaishvili put Ulsan ahead after 13 minutes at Jeonju World Cup Stadium, only for Han Kyo-won to level for Jeonbuk, champions in 2006 and 2016.
Just before the break, Yun Il-lok restored Ulsan's lead. It didn't last long with Jeonbuk hitting back, this time through Takahiro Kunimoto early in the second half.
After 101 minutes, South Korea international Lee Dong-gyeong hit the winner with a fierce shot from outside the area.
Next up for Ulsan is a semi-final on Wednesday against Pohang Steelers, another South Korean opponent.
Pohang, aiming for a record fourth Asian title, defeated Nagoya Grampus of Japan 3-0.
Lim Sang-hyub opened the scoring eight minutes into the second half and with 20 minutes remaining, Lee Seung-mo added a second. Lim's second in injury time sealed the victory.
The winner will face a team from Saudi Arabia in the final on 23 November.
Three-time champions Al-Hilal defeated Persepolis of Iran 3-0 in Riyadh thanks to two goals from former France international striker Bafetimbi Gomis and a long-range strike from Salem Al-Dawsari.
Al-Hilal will face Riyadh rival Al-Nassr in Tuesday's semi-final. Al-Nassr, in their first game under new Portuguese coach Pedro Emanuel, thrashed Al-Wahda of the United Arab Emirates 5-1.
The final will take place in Riyadh.