US ambassador killed in Libya: investigators probe whether Benghazi assault was planned Analysts and former jihadists suggested the attack might have been well-planned and linked to a call earlier in the day by the head of al-Qaeda, Ayman al-Zawahiri, for vengeance for the death of his Libyan deputy in a US drone strike in June. The White House is investigating whether these suggestions could be true. Speaking outside the White House on Wednesday, Mr Obama confirmed that a 50-strong US marine antiterrorist security team had been dispatched to Libya to bolster security and aid efforts to find those responsible. He paid tribute to the work of Mr Stevens, who had led American diplomatic efforts to liberate Benghazi last year. The attacks were swiftly condemned as "cowardly" by Libya's interim government and by the international community. William Hague, the Foreign Secretary, who arrived in Iraq last night following a stop in Egypt, said it was "the sort of attack that won't achieve anything." David Cameron called the attack "senseless." White House staff lowered the U.S. flag to half mast on the roof of the White House in Washington following the death of U.S. Ambassador to Libya, Chris Stevens (Reuters) Mr Stevens is the first US ambassador to be killed in the line of duty since Adolph Dubs, an envoy to Afghanistan, who was kidnapped and killed during an attempt to rescue him in 1979. US officials said that a grenade had set a building inside the walled consulate compound ablaze, leaving the Americans facing both a fire inside and attackers outside. According to reports that emerged overnight, the ambassador became separated from the rest of his staff, including his security detail, during an attempt to escape. He eventually made his way to the roof of the building and succumbed to smoke inhalation, the official said. His body was taken to hospital by Libyans, a moment captured in distressing photographs which circulated the internet, and only retrieved later by a team of marines sent from the embassy in Tripoli as reinforcements. In the meantime, Mr Smith and two American security officials were shot dead as the remainder of the staff made their way to safety. Doctors at the Benghazi Medical Centre said Mr Stevens had been at the point of death when he was brought in by several friendly Libyans. The Quilliam Foundation, an anti-extremist think tank in London, speculated in a statement that the attacks could have been linked by a promise this week by Ayman al-Zawahiri to avenge the death of his deputy, Abu Yahya al-Libi, who was killed in a drone strike in June. Parts of the U.S. Consulate in Benghazi are set on fire during a protest by an armed group (Reuters) A group called the "Imprisoned Omar Abdul Rahman Brigades," which attacked both the Red Cross office and the US consulate in Benghazi earlier this year, was being put forward as a leading suspect for the attacks. Its links to a broader Islamist movement called the Ansar al-Sharia will also be the focus of attention. However, local residents claimed that the protest turned violent after rumours swept the crowd that it was being fired on itself from inside the consulate, or by the consulate's Libyan security detail. The performance of that detail will also be of concern both to the new Libyan government, which elected a prime minister last night, and to its western backers. The detail, of about 40 men, appears to have done little to fight back. The commander of one of the main pro-government defence forces operating in Benghazi, the Libya Shield Brigade, told Reuters news agency that they may have felt the protesters were justified because of the content of the film. "I first of all place the blame on the United States itself for allowing such a movie to be produced," the commander, Wissam Buhmeid, said. This was the product of the anger of Muslims. He added: "The deaths and injuries and attacks are all nothing compared to insulting the Prophet." Even the head of the brigade that acts as an interim police force in Benghazi, Abdel-Salam al-Bargathi, said that although they had "gone too far" the protests were a "very natural reaction to the insult to the Prophet." US military officials said they were preparing to launch reconnaissance drones over eastern Libya to assist local security forces in hunting down the militants responsible. The FBI was also reported to be involved. The US said it had evacuated most of its diplomatic staff from Libya, flying them to Germany. The US was bracing for further flashpoints around the Islamic world as the film, Innocence of Muslims, which also provoked protests outside the US embassy in Cairo, spread across the Middle East on the internet. Earlier on Tuesday, protesters had climbed the walls of the US embassy in Cairo, torn down the American flag and replaced it with an Islamist banner. There were more protests on Wednesday evening, though on this occasion the crowd was dispersed by police using tear gas. The Afghan government reportedly attempted to block YouTube to stop the film being shared as the Taliban vowed to "take revenge" on US troops.