Having lost the first leg in Iran, Al Ain – beaten finalist last season – did not look back after Caio's volley gave his side the lead after 27 minutes, producing a supreme performance.

Caio struck again before half-time and two impressive finishes from Omar Abdulrahman as well as a strike from Lee Myung-joo had the side from United Arab Emirates five up on the night by the hour mark.

Nassir Al Shamrani made it six for Al Ain, with Kaveh Rezaei's late free-kick for Esteghlal the visitor's only resistance as it exited the competition.

In Tuesday's (AEST) other game, two-time runners-up Al-Ahli of Saudi Arabia defeated its namesake Al-Ahli from the United Arab Emirates 3-1 in the second leg of its last-16 tie, sealing a 4-2 aggregate victory.

After the first encounter ended one apiece, Christian Gross' side seized control with two goals in the first 24 minutes, Taiseer Al Jassam's close-range strike followed up by Hussain Al-Mogahwi's impressive effort into the top corner.

Makhete Diop was sent off for the home side after receiving a second yellow card just before the hour mark, denting their hopes of a comeback.

And Saad Abdulameer sealed the Saudis' progress with a penalty after Salman Muwashar had been brought down by home goalkeeper Majed Naser.  

Asamoah Gyan scored a stoppage-time spot-kick for the trailing Emirati side, but it was far too little, too late.