Entourage star Adrian Grenier has been attacked online for the 'classless' 9/11 tribute he shared on social media.

The 39-year-old actor made the post on Friday, writing: 'R.I.P. the 2,996 Americans who died in 9/11. R.I.P. the 1,455,590 innocent Iraqis who died during the U.S. invasion for something they didn't do.'

The now-deleted Instagram post included an image of the Twin Towers, reported Fox News.

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Entourage star Adrian Grenier, 39, (left) has received backlash for a 'classless' 9/11 tribute (right)

Grenier (pictured on set for the HBO series Entourage) deleted the post following criticism

The post, which was shared in a link on his Twitter, received criticism from Twitters users, who said it was 'classless' and a 'slap in the face' to the 9/11 victims.

'Today was not the day to post this,' said one social-media user. 'Classless. You have no idea how families feel everyday on this day and everyday period.'

Another wrote: 'That sure was a slap in the face at the 9/11 victims! But when your (sic) a second tier actor, it's I need attention time,' one user wrote.

Others called him out for deleting the post.

'Nice job coward. Real conviction you have, deleting your post and all. #911Anniversary,' one tweet said.

That same day, Grenier - who plays Vinnie Chase in the HBO series - had shared other images on Instagram to commemorate the 14th anniversary of 9/11.

Among them was a tribute that read: 'In challenging moments and times of mourning, we must seek perspective to help us find peace within our choices forward. #911.'

Last month, the outspoken environmentalist was critical of Donald Trump's position on global warming - calling it 'extremely destructive', according to the New York Post.

One user said the post was 'classless' and said the actor did not have an idea how families 'feel everyday on this day and everyday period'

'That sure was a slap in the face at the 9/11 victims! But when you a second tier actor, it's I need attention time #9-11-01,' another user wrote

After Grenier deleted the post, a user called him a coward for not having 'conviction' in his views

'I appreciate your post of this meme as it showed your true character and utter ignorance. #fail,' a user wrote