HARARE, Zimbabwe (CNN)  -- President Robert Mugabe was sworn in Sunday after the Zimbabwe Electoral Commission declared he overwhelmingly won the country's disputed runoff election. "I, Robert Gabriel Mugabe, do swear that I will well and truly serve Zimbabwe in the office of president, so help me God," Mugabe said at the State House complex in Harare, standing  before a red-robed judge wearing a white wig. His words were met with loud applause. The international community has roundly called the election -- allegedly marred by violence and vote rigging -- a "sham." Many voters expressed fear of government retaliation if they did not take part in the vote to extend Mugabe's rule. Some said they were required to report the serial numbers on their ballots to Mugabe's Zimbabwe African National Union -- Patriotic Front. Watch as Mugabe gets sworn in »
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NEW: Mugabe swears to "truly serve Zimbabwe ... so help me God"
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Opposition denounces election as "a one-man race, a one-man circus"
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Observers say Zimbabweans "dragged" to polling stations, forced to vote
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Election has been condemned as a sham after opposition candidate withdrew
"The information that we have right now is that @placeholder is proceeding with impunity, completely disregarding the world opinion," he said.