Washington/Benghazi - President Barack Obama vowed on Wednesday to "bring to justice" the Islamist gunmen responsible for a ferocious assault that killed the US ambassador to Libya and three other Americans - an attack that may have been organised in advance.
Ambassador Christopher Stevens and the other Americans died after the gunmen attacked the lightly fortified US consulate and a safe house refuge in Benghazi on Tuesday night. The attackers were part of a mob blaming America for a film they said insulted the Prophet Mohammad.
Obama said he had ordered an increase in security at US diplomatic posts around the globe following the assault.
The US consulate was overrun and torched in a military-style assault, the ambassador left lost and dying alone in the smoke while rescuers ran into a deadly ambush as they sought to save survivors. The attackers used guns, mortars and grenades. US and Libyan officials said the attack may have been planned in advance.
The violence in the eastern city, a cradle of Libya's US-backed uprising against Muammar Gaddafi last year, came on the 11th anniversary of al Qaeda's attacks on the United States on September 11, 2001. Another assault was mounted on the US embassy in Cairo on Tuesday in which protesters, who included Islamists and teenage soccer fans, tore down and burned a US flag.
In Cairo, security forces late on Wednesday fired tear gas to disperse more stone-throwing demonstrators near the embassy. Live TV showed hundreds of demonstrators at the US embassy.
Stevens, a 52-year-old California-born diplomat who spent a career operating in perilous places, became the first American ambassador killed in an attack since Adolph Dubs, the US envoy to Afghanistan, died in a 1979 kidnapping attempt.
A Libyan doctor pronounced him dead of smoke inhalation. US information technology specialist Sean Smith and two other Americans who have not yet been identified also were killed.
Among the assailants, Libyans identified units of a heavily armed local Islamist group, Ansar al-Sharia, which sympathises with al-Qaeda and derides Libya's US-backed bid for democracy.
US government officials said the Benghazi attack may have been planned in advance, also adding that there were indications that Ansar al-Sharia - which translates as Supporters of Islamic Law - may have been involved.