The Scottish giants welcome the LaLiga side in the Champions League on Wednesday night as they look for their first points in the competition this season.
Before the tie, supporters had been asked by the club not to bring in any banners relating to the ongoing conflict between Israel and Hamas.
In a statement, Celtic said players and coaching staff from both teams would wear black armbands 'as a show of respect and support for all those affected by the conflict'.
But the club also said banners, flags and symbols relating to the Israel-Hamas war 'should not be displayed at Celtic Park at this time'.
However, these orders were defied emphatically.
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Coloured bin bags organised to resemble the Palestine flag were placed in the stands before kick-off.
A number of Palestine flags were then spotted in the crowd as the match began.
Ahead of the game, a section of supporters stated they would give flags to supporters.
The group, known as the Green Brigade, have already been banned by Celtic after they displayed flags in the wake of the attacks in Israel and Gaza.
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In a statement, the Green Brigade said the ban from the club was 'motivated by a desire to quash political expression within the Celtic support'.
They also said they still had an 'unshakeable belief' supporters have a right to express political beliefs.
Celtic started the match strongly with Kyogo Furuhashi putting them ahead on four minutes.
Antoine Griezmann equalised from the spot in the 25th minute but the Hoops retook the lead through Luis Palma three minutes later as Celtic went in at half time 2-1 up.
However, Alvaro Morata pulled his side back level in the second half to make it 2-2, with the Spanish side holding on to a point despite going down to ten men following Rodrigo De Paul's red card.