WASHINGTON - US President Barack Obama on Wednesday called his Afghan counterpart Hamid Karzai over how to contain the spillover into Afghanistan of the deadly attack on the US consulate in Libya's eastern city of Benghazi.

"President Karzai expressed condolences for the tragic loss of American life and the presidents discussed the importance of working together to help ensure that the circumstances that led to the violence in Libya and Egypt do not pose a threat to US forces or Afghans," the White House said in a statement.

US Ambassador to Libya Chris Stevens and three other diplomats was killed Tuesday night after hundreds of protesters, angered by an alleged US-made movie that they say insults Prophet Mohammed, broke into and set ablaze the US consulate building.

Protesters stormed as well into the US embassy in Cairo on Tuesday and burned an American flag, while in Tunisia police were reportedly firing teargas to disperse demonstrators outside the US embassy on Wednesday night.

Mindful of the riots that killed some 40 persons earlier this year after US troops burned copies of the Quran at a military base in Afghanistan, the Afghan authorities have moved to shut down the YouTube site on which one clip of the movie was posted, and Karzai denounced the film-making as a "devilish act".