The Iranians held a 2-1 advantage from last week's quarter-final first leg in Esfahan but the one-goal lead was erased after nine minutes at the Steelyard as Pohang went ahead through Kim Jae-sung.

Mota's beautifully threaded ball set Jung Hong-young free down the left and his cutback was sidefooted into the back of the net by Kim from 10 yards to put the hosts in position to qualify thanks to the away goals rule.

Pohang dominated the game and Seol Ki-hyeon was guilty of an incredible miss with 20 minutes to go as he sprung the Zob Ahan offside trap to latch on to a long ball down the left, and beat onrushing goalkeeper Shahabaldin Gordan but then fired over an empty goal from seven yards.

The hosts were made to pay in the 80th minute when Khalatbari buried his first chance of the match.

The Iran striker turned a defender to collect Ghasem Hadadifar's pass, knocked the ball out of his feet with his first touch and with his second smashed a low right-footed drive across goalkeeper Shin Hwa-yong and in via the far post.

Mahdi Rajabzadeh was then sent off three minutes from the end, collecting a second booking for time-wasting while off the pitch on a stretcher, but Zob Ahan held on to go through 3-2 on aggregate.

"We concentrated on attacking in the second half. My players did their best," said boss Mansour Ebrahimzadeh, who went on to condemn Rajabzadeh's actions.

"If he was injured seriously there was nothing we can do about it but even for me, It was too much," he added.

"I have to admit it, I think Rajabzadeh did the wrong thing."

At Suwon World Cup Stadium, Suwon Bluewings almost pulled off an amazing fightback but fell just short against Seongnam Ilhwa Chunma.

Needing to win 3-0 after a 4-1 defeat at Tancheon Sports Complex, the hosts went ahead after 32 minutes as Yeom Ki-hyun lashed in a 25-yard free-kick.

Lee Sang-ho scored a second for Suwon on the hour mark when the striker stroked home Marcio's pass, but they were unable to add to their tally and Seongnam progressed 4-3 on aggregate.

"I feel a little uncomfortable that we progressed to the semi-final by losing," said Seongnam boss Shin Tae-young.

"In the game, Suwon played well in all aspects. We needed the big win from the first leg to get through."

Al Gharafa were denied a place in the semi-finals as a remarkable comeback was sunk by two Al Hilal goals deep into extra time.

Trailing 3-0 from the first-leg against arguably the strongest side left in the competition, the hosts' task looked almost insurmountable but the deficit was erased in a breathtaking first-half at Al Gharafa Stadium.

Mirghani Al Zaini opened the scoring after just two minutes when he collected Clemerson's pass, beat a defender and fired past Al Hilal keeper Hasan Al Otaibi.

Iraq international Younes Mahmoud then headed in the second goal from a corner in the 38th minute before Othman El Assas drew Al Gharafa level on aggregate with a fine free-kick two minutes later.

Al Hilal missed a number of chances in the second-half and looked set to pay for their profligacy when Mahmoud claimed Al Gharafa's fourth 11 minutes into extra time.

However, Yasser Al Qahtani netted a crucial goal for Al Hilal two minutes from the end and Eysa Mohammed added a second one minute later to break Qatari hearts as the Saudis progressed 5-4 on aggregate.

"We wanted to keep our concentration in the first 20 minutes of the match but we conceded a goal in only the second minute through some fantastic motivation shown by the Gharafa players," said Al Hilal coach Eric Gerets.

"After the first goal, we just did not play well as a team. We forgot how to play football after the first goal. It was a tough match and I am very happy we have qualified.

"We needed a miracle and we got it in the last minutes. Right now I am just thinking of going back to the hotel to get some sleep. A lot of things went wrong."

Al Shabab made it two teams from Saudi Arabia into the semi-finals as they qualified despite losing 1-0 to Jeonbuk Motors at King Fahd International Stadium.

Kim Jee-wong's long-range strike midway through the first-half gave the visitors hope they could overturn a two-goal deficit from the first leg of the quarter-final encounter following a disappointing defeat in Korea.

But they could not find the elusive second they needed and went out 2-1 on aggregate.

"The game was really hard for us and there was a lot of pressure on our players," said Al Shabab coach Jorge Fossati.

"I'm satisfied with the performance despite the defeat. The good win that we had in Korea Republic helped us a lot to advance to the semi-finals.

"Any team who plays away tries to get a draw or at least a narrow defeat but we did a good job of taking a two goal advantage. But things we really critical tonight."