The Libyan government failed to deliver security reinforcements at the US diplomatic post in Benghazi on the day of an attack that killed US Ambassador Chris Stevens, according to a report by Foreign Policy magazine.
Quoting from documents recovered from the former US compound weeks after the attack, Foreign Policy reported that US officials had serious security concerns in the hours leading up to the fatal attack.
The documents suggested Libyan police were often absent, and that at least one of the officers may have been complicit in planning the attack.
In an unsigned letter written on September 11, 2012, to Mohamed Obeidi, head of the local office of the foreign affairs minister, its author wrote:
"Finally, early this morning at 0643, September 11, 2012, one of our diligent guards made a troubling report. Near our main gate, a member of the police force was seen in the upper level of a building across from our compound. It is reported that this person was photographing the inside of the US special mission and furthermore that this person was part of the police unit sent to protect the mission. The police car stationed where this event occurred was number 322."
The report reinforced accusations made by local tribal leaders and army officials in interviews with Al Jazeera in the days following the attack that the national government was at fault for failing to provide adequate security.
The Libyan security forces are in serious disarray, and in the weeks following the attack there were widespread protests across the country with civilians urging the government to make the rebuilding of the police force and army a top priority.
The revelations come as the debate over Benghazi continues to feature in the US presidential election campaign.
On Thursday, a senior American intelligence official told the Reuters news agency that CIA officials on the ground in Libya dispatched security forces to the US diplomatic mission in Benghazi within 25 minutes and made other key decisions about how to respond to the waves of attacks on US installations on September 11,
Officials in Washington monitored events through message traffic and a hovering US military drone but did not interfere with or reject requests for help from officials in the line of fire, the official said on Thursday.
The information emerged as officials made available a timeline chronicling the US response to the Benghazi attacks in which Christopher Stevens, the US ambassador to Libya, and three other American officials died.
The material appears to refute claims by critics that officials in Washington delayed sending help to the besieged personnel.
The handling of the attack by the Obama administration and CIA has come under sharp criticism by supporters of Republican challenger Mitt Romney during the campaign ahead of the presidential election on November 6.
The senior intelligence official said that CIA officers in Benghazi, "responded to the situation on the night of 11 and 12 September as quickly and as effectively as possible”.
"The security officers in particular were genuine heroes. They quickly tried to rally additional local support and heavier weapons, and when that could not be accomplished within minutes, they still moved in and put their own lives on the line to save their comrades," the official said.
"At every level in the chain of command, from the senior officers in Libya to the most senior officials in Washington, everyone was fully engaged in trying to provide whatever help they could," the official said.
"There was no second-guessing those decisions being made on the ground, by people at every US organisation that could play a role in assisting those in danger. There were no orders to anybody to stand down in providing support," the official added.
Intelligence and other administration officials expressed particular dismay about a report on Fox News last week that alleged that armed CIA operatives near the US compound in Benghazi were repeatedly told to "stand down" after asking for permission to assist on the night of September 11 and were also refused military backup by the CIA chain of command.
Following the initial broadcast of the Fox News report, Jennifer Youngblood, a CIA spokesperson, denied that CIA had ever turned down requests for help from US personnel in Benghazi.
"No one at any level in the CIA told anybody not to help those in need; claims to the contrary are simply inaccurate," Youngblood said.