US Defence Secretary Donald Rumsfeld was repeatedly interrupted and heckled by anti-war protesters during a speech.
One protester, retired CIA analyst Ray McGovern, accused Mr Rumsfeld of lying to the American people about the presence of WMD in Iraq before the war.
Mr Rumsfeld rejected the accusation and said the Bush administration based its assertions on existing intelligence.
The outbursts were more severe than the previous protests Mr Rumsfeld has faced over the Iraq war, correspondents say.
It comes weeks after Mr Rumsfeld was called upon to resign by six retired senior US military officers for his handling of the war.
The defence secretary was giving a speech on military alliances in Atlanta, Georgia, when he was interrupted by hecklers, including one who carried a sign saying: "Guilty! of war crimes".
Three protesters were escorted away by security, while a fourth stood in the middle of the room with his back to Mr Rumsfeld in silent protest, the Associated Press reports.
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