UEFA opens disciplinary case against Wenger
Wenger sat in the directors' box during Tuesday's 1-0 home win over Udinese in the first leg of their Champions League play-off, serving a one-match ban, and communicated with first-team coach Boro Primorac via his phone.
"According to the UEFA disciplinary regulations, a manager may not communicate with his team during the match for which he is suspended and may follow the game from the stands only," European football's governing body said in a statement.
Wenger, who said earlier this week he was confused by the rules, could now face a possible extension to his ban when the case is discussed on Monday.
The Frenchman had said Arsenal had been told communication with the bench was allowed during the match but UEFA officials then ordered it to stop at half-time.
Wenger had been suspended for comments made about referee Massimo Busacca after last season's Champions League last 16 second-leg defeat by Barcelona.
Arsenal said on their website they would be appealing the UEFA decision, which comes before the Gunners head to Italy on Wednesday for the second leg of the play-off against Udinese.