Victor Simoes and Kim had put the home side in command early on before Takahiro Futagawa and Ryuji Bando restored parity.

Michihiro Yasuda then put Gamba in front for the first time before Kim Tae-su equalised from the spot.

Bando then scored a 76th-minute winner that puts Gamba's challenge for a place in the knockout stages back on track, after being held to a surprise draw by Thai champions Chonburi in their opening game.

Chunnam, who lost their opener against Melbourne Victory, are without a point in the competition so far.

It could have been a lot different for the hosts who took the lead after four minutes when a header from Tae-su was not dealt with by defender Satoshi Yamaguchi and Simoes raced in to powerfully finish past goalkeeper Yosuke Fujigaya.

They had further chances to extend the lead, with Fuyigaya saving a effort from Kim, before the captain scored the second goal in the 27th minute. He rose well to head home from close range at the far post.

This shocked the visitors into life and four minutes later they gave themselves a lifeline. Futugawa thought quickly when picking the ball up and deftly curled the ball beyond the left hand of Chunnam goalkeeper Yeom Donggyun.

Akira Nishino's side dominated the remainder of the half but they had to wait until nine minutes after the restart before equalising. It was Bando who was on hand to slot home from close range, after Lucas steered Endo's corner into his path.

Five minutes later Gamba were in front. Yasuda's right foot drive had power and Yeom could only push the ball into net, however there were yet more twists to come.

Less than a minute later, Chunnam were awarded a penalty when Hideo Hashimoto upended Kim Mung Woon in the penalty area and Tae-su rolled home from the resulting spot-kick.

However, Gamba were not to be denied their comeback victory and Yasuda's low cross was perfectly placed for Bando who made no mistake to score his second goal from inside the six-yard box.