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LASK trailed 3-0 heading into the second leg at Raiffeisen Arena, and it fell even further behind when Callum McGregor put Celtic into a 21st-minute lead in the match. 

But Moses Usor, Robert Ljubicic and Adeniran hauled LASK within one, and it forced extra time in the 90th minute when Florian Flecker's header survived a VAR review. 

Adeniran picked out the bottom-left corner in the second period of extra time to seal the win, while also seeing a penalty saved by Viljami Sinisalo six minutes later. 

LASK started brightly but fell behind to McGregor's strike, which deflected off Alemao and bounced over Lukas Jungwirth's dive, but the host responded emphatically. 

Benjamin Nygren's blind pass back to his goalkeeper Sinisalo was ruthlessly punished by Usor, who rolled the ball into the back of the net with 32 minutes on the clock. 

The host pulled ahead in the match three minutes after the restart when Ljubicic was allowed time and space on the edge of the box to pick out the bottom-right corner. 

Adeniran then got LASK to within one of Celtic on aggregate when he curled a sensational effort past Sinisalo from 25 yards out just before the hour to set up a tense finish. 

Celtic's defence was eventually breached late in the day when Krystof Danek's header was saved by Sinisalo, with Flecker on hand to tuck in the rebound, with the goal given after a VAR review for offside against the LASK substitute. 

LASK completed the turnaround in the second period of extra time when Adeniran's low drive nestled into the back of the net, and he could have scored a hat-trick when Danek was brought down in the box by Reo Hatate, but his spot-kick was saved by Sinisalo, though the host held on for a remarkable victory.