The build-up to Atletico Madrid's Champions League clash with Bayer Leverkusen was marred by serious incidents between home fans and the police prior to kick-off.
Around the Vicente Calderon, supporters found themselves boxed in by security forces, as they sang boisterously ahead of Wednesday's second leg.
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And the tense atmosphere eventually erupted in violence, with bottles and other projectiles flying.
Police forces then entered into the fray with a heavy show of strength, with several fans arrested and others on the receiving end of batons in an unsavoury melee.
Atletico enjoyed a 4-2 aggregate lead ahead of kick off after a fine victory in Germany in February's first leg.