The defending champion Germany failed to make it to the knockout stage at the 2018 World Cup, suffering the earliest exit in 80 years.

Ozil, 29, was a key member of Germany's World Cup championship team in 2014 and has been voted by fans as the team's player of the year five times since 2011.

He appeared in 92 matches with the German national football team, and was widely seen as one of the best midfielders of his age.

In 2010, he received Germany's prestigious Bambi Award as an example of successful integration into German society.

Voicing disappointment on his Twitter account on Sunday, the footballer asked: "I was born and educated in Germany, so why don't people accept that I'm German?"

Turkish Football Federation Chair Yildirim Demiroren voiced support for the Turkish-German football star and condemned the treatment against him.

Meanwhile, the ruling Justice and Development Party Spokesman Mahir Unal welcomed Ozil's resignation from the German national team, and accused some circles in Germany of aiming at assimilation.

"Some approaches in Germany after Ozil's announcement show us that there is an intention of assimilation under the cover of integration," Unal told reporters on Monday.

He accused Europe of "clashing with values that it was built on" and that Turkey is "uneasy" with this trend.

On the other hand, Ulrike Demmer, spokeswoman for German Chancellor Angela Merkel, said Merkel "values Mesut Ozil highly."

She said Ozil had "made a decision that has to be respected," insisting that "Germany is an open country in which people with immigrant backgrounds are very welcome."