President Barack Obama on Wednesday strongly condemned the killing of the US ambassador to Libya and three other embassy staff, calling it an "outrageous attack," and ordered stepped-up security at US diplomatic posts worldwide.
The targeting of US diplomats, in militant violence sparked by a U.S.-made film seen as insulting the Prophet Mohammad, could raise questions about Obama's policy toward Libya in the post-Gaddafi era as he seeks re-election in November.
Obama, apparently seeking to seize the initiative in the aftermath of the attack, planned to speak to reporters in the White House Rose Garden at 10:35 a.m. EDT with Secretary of State Hillary Clinton at his side.
"I have directed my administration to provide all necessary resources to support the security of our personnel in Libya and to increase security at our diplomatic posts around the globe," Obama said in a written statement.
Ambassador Chris Stevens and three other US diplomats were killed as they rushed away from a consulate building in Benghazi, stormed by al Qaeda-linked gunmen blaming America for the film that they said mocked the Prophet of Islam.
Sean Smith, a foreign service information management officer, was identified as one of the diplomats killed, in a statement by Clinton. The names of the two others were withheld while the government notified their families.
Stevens, a 21-year veteran of the foreign service, was one of the first American officials on the ground in Benghazi during the uprising against former Libyan dictator Muammar Gaddafi last year.
Gaddafi was ousted by rebel forces backed by NATO air power in August 2011 and was killed in October after months as a fugitive.
Obama had hailed Libya's election in July as a milestone in its post-Gaddafi democratic transition and pledged the United States would act as a partner even as he cautioned that there would still be difficult challenges ahead.
He had opted for a cautious strategy that steered clear of a dominant role for the US military and faced criticism from Republican opponents at home for what was described as "leading from behind."
Before the full death toll and details of the Libya attack were known, Obama's Republican presidential challenger, Mitt Romney, on Tuesday night criticized the Obama administration's initial response to violent attacks at U.S. diplomatic missions in Libya as well as Egypt.
Pushing back hard, Obama campaign spokesman Ben LaBolt criticized Romney for making a "political attack" at a time when the country was "confronting the tragic death of one of our diplomatic officers in Libya."
Obama was notified on Tuesday night that Stevens was unaccounted for and was told on Wednesday morning of his death, a White House official said.
"I strongly condemn the outrageous attack on our diplomatic facility in Benghazi, which took the lives of four Americans, including Ambassador Chris Stevens," Obama said.
"Right now, the American people have the families of those we lost in our thoughts and prayers. They exemplified America's commitment to freedom, justice and partnership with nations and people around the globe and stand in stark contrast to those who callously took their lives," he said.
Gunmen had attacked and set fire to the US consulate in the eastern city of Benghazi, the cradle of last year's uprising against Muammar Gaddafi's 42-year rule, late on Tuesday evening as another assault was mounted on the U.S. embassy in Cairo.
The California-born ambassador was trying to leave the consulate building for a safer location as part of an evacuation when gunmen launched an intense attack, apparently forcing security personnel to withdraw.
A Libyan official said the diplomats were killed when "gunmen fired rockets in their direction." White House and State Department statements gave no details on exactly how the four were killed.
"While the United States rejects efforts to denigrate the religious beliefs of others, we must all unequivocally oppose the kind of senseless violence that took the lives of these public servants," Obama said.
Clinton also denounced the attack, calling it "vicious and violent." Romney also condemned the attack and said the attack on US mission in Libya is 'outrageous,' 'disgusting' and heartbreaking.