The Bundesliga side announced the decision in a brief statement on Friday, which read: "1. FSV Mainz 05 terminated their contract with Anwar El Ghazi with immediate effect on Friday. The club has taken this action in response to comments and posts from the player on social media."
But the Dutch winger remained unrepentant, taking to Instagram to post: "The loss of my livelihood is nothing when compared to the hell being unleashed on the innocent and vulnerable in Gaza."
Mainz had suspended El Ghazi last month after the player's Instagram post expressing support for the plight of Palestinians caught up in the current conflict between Israel and Hamas.
Matters appeared to be heading to a resolution on Monday when Mainz lifted the suspension, stating that the player had been given a warning and had showed remorse over the since-deleted post.
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But the issue escalated again on Wednesday when El Ghazi made a statement contradicting the club, writing: “I do not regret or have any remorse for my position. I do not distance myself from what I said and I stand, today and always until my last breath, for humanity and the oppressed.”
Mainz responded to that statement by expressing surprise and vowing to "examine the fact from a legal standpoint," before arriving at the decision to terminate El Ghazi's contract.
The 28-year-old joined Mainz in the summer after spells with Ajax, Lille, Aston Villa and PSV. Before the suspension he made just three substitute appearances for his new club, who remain bottom of the table ahead of this weekend's clash with RB Leipzig.