WASHINGTON - Leaders in Egypt, Libya, Yemen and Tunisia, which have all seen attacks on US diplomatic missions this week, must do all they can to restore calm and reject "the tyranny of a mob," US Secretary of State Hillary Clinton said on Friday.

"This has been a difficult week," Clinton said as she spoke at a ceremony to mark the return of the remains of four Americans killed in an attack on the US consulate in Benghazi, Libya on Tuesday.

"We've seen the heavy assault on our post in Benghazi that took the lives of those brave men. We've seen rage and violence directed at America embassies over an awful Internet video that we had nothing to do with, she added, standing in front of the flag-draped caskets of the four men.

"It is hard for the American people to make sense of that because it is senseless and it is totally unacceptable," she added, echoing comments earlier this week in which she said there was no justification for responding with violence to the video, which she has called "disgusting and reprehensible."

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