(CNN) Mitt Romney led fresh Republican attacks on Friday over Vice President Joe Biden’s debate remark about security concerns at the U.S. diplomatic compound in Libya where four Americans – including Ambassador Christopher Stevens — were killed in a terrorist attack.

The GOP presidential challenger accused Biden of contradicting State Department officials when he said at Thursday’s debate against Romney’s running mate, Rep. Paul Ryan, that “we weren’t told they wanted more security” at the diplomatic facility in Benghazi.

The mission came under attack by armed militants on the 11th anniversary of the September 2001 al Qaeda attacks on New York and Washington.

However, State Department officials told a congressional hearing on Wednesday that they requested more security but were turned down by headquarters in Washington.

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