Inter Milan asked on Wednesday for UEFA to investigate why a large number of their supporters were not allowed into Porto's stadium to watch their team reach the Champions League quarter-finals.
Around 1,000 Inter supporters were held outside the Estadio do Dragao on Tuesday despite holding valid tickets, as they had been purchased for home supporter sections of the ground.
They were corralled into a cramped tunnel near the away end until the gates were shut at the end of the first half.
"FC Internazionale Milano asks UEFA to intervene so that light is shed on what happened and that situations of this kind, contrary to the key principles of sportsmanship, equality and inclusion, are never repeated," Inter said in a statement.
Inter blasted the handling of the situation as exposing their fans, including children, to "potential danger".
The Serie A club held Porto to a goalless draw and qualified for the last eight of the Champions League for the first time since 2011.
