Nasri launched an X-rated rant at French reporters after they were beaten by Spain in their quarter-final clash on Saturday night.
Nasri then turned on a reporter from Agence France Presse (AFP) when asked for his reaction to the defeat, allegedly saying: "You are looking for s**t, looking for trouble. F*** you, go f*** your mother, you son of a b****."
He then offered the reporter outside, before being hustled away to the team coach.
Blanc: "There is a problem between the Press and Samir Nasri. It was embarrassing and regrettable. If it is true, it is disrespectful to the journalist.
"This is unfortunate for his personal image and that of the national team. I've already told Samir what I had to say, but obviously the message did not go well."