Club president Massimo Moratti and Mancini had met on Tuesday, but the club made no comment for 48 hours following those talks.
"FC Internazionale have informed Roberto Mancini that he has been sacked as coach," said the Inter statement.
"In particular because of the comments made by the coach at the end of the Inter-Liverpool match."
Mancini joined Inter in 2004 and as well as those three Serie A titles he also guided the club to successive Italian Cup victories in 2005 and 2006.
On Wednesday Mancini's agent Maurizio De Giorgis told BBC Sport: "He no longer works for Internazionale. He's available for work if he gets a phone call."
Before moving to Inter, Mancini had previously coached Fiorentina and Lazio.
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