Heavily armed militants used a protest against an anti-Islam film as a cover and may have had inside help in their deadly attack on the US Consulate, a senior Libyan official says.
As Libya announced the first four arrests, the clearest picture yet emerged of a two-pronged assault with militants screaming "God is great!" as they scaled the consulate's outer walls and descended on the compound's main building.
Killed in the attack were US Ambassador Chris Stevens, information management officer Sean Smith, private security guard Glen Doherty, another American who has yet to be identified and a number of Libyans.
Eastern Libya's deputy interior minister, Wanis el-Sharef, said a mob first stormed the consulate on Tuesday night and then, hours later, raided a safe house in the compound just as US and Libyan security arrived to evacuate the staff.
That suggested, el-Sharef said, that infiltrators within the security forces may have tipped off the militants about the safe house's location.
The attacks were suspected to have been timed to coincide with the 11th anniversary of the September 11 terrorist strike in the United States, el-Sharef said, with the militants using the film protest by Libyan civilians to mask their action.
El-Sharef said four people were arrested at their homes on Thursday, but refused to give further details.
He said it was too early to say if the suspects belonged to a particular group or what their motive was.
Libya's new prime minister, Mustafa Abu-Shakour, said authorities were looking for more suspects.
One of five private security guards at the consulate said the surprise attack began around 9.30pm when several grenades that were lobbed over the outer wall exploded in the compound and bullets rained down.
The guard was wounded in the left leg from shrapnel.
He said he was lying on the ground, bleeding and in pain when a bearded gunman came down the wall and shot him twice in the right leg, screaming: "You infidel, you are defending infidels!"
"Later, someone asked me who I was. I said I was the gardener and then I passed out. I woke up in hospital," said the guard, who spoke from his bed at a Benghazi hospital.
The witness account came as protests against the obscure film Innocence of Muslims continued in the Middle East.
Four people were killed when an angry throng broke into the US Embassy in Yemen.
Clashes between security forces and demonstrators near the fortress-like embassy compound in the heart of Cairo left nearly 200 people injured and two police trucks burned.
No one has claimed responsibility for the Libya attack.
Some Libyan officials have accused hardline Islamist militia, the Ansar al-Shariah Brigades.
A spokesman for the group lavishly praised the assault for "protecting the faith and fighting for the victory of God Almighty". But he said the brigades "did not participate as an organisation. This was a popular uprising."
Adding to the confusion surrounding the attack is that it targeted the United States, a nation that played a key role in ridding the oil-rich, mostly desert nation of dictator Muammar Gaddafi.
Washington also took the lead in launching the months-long NATO air campaign that crippled the late leader's forces.
Stevens was credited by Libyans for organising a political front made up of opposition groups to unite the uprising.
Stevens probably died of asphyxiation following a grenade explosion that started a fire, el-Sharef said, echoing what the Libyan doctor to whom Stevens' body was taken said on Wednesday.
His account was corroborated by local journalist Ibrahim Hadya, who was at the scene.
He said the consulate was stormed just as the evacuation was under way, with staff members smuggled out a side door that opens to a street other than the one where the militants and protesters gathered.
El-Sharef said the original plan was for a separate Libyan security unit to escort the evacuees to the airport.
Instead, the joint unit went from the airport to the safe house, possibly because they were under the impression they were dealing with a hostage situation, he said. The militant attack coincided with the joint team's arrival at the safe house, he said.
That the attackers knew the safe house's location suggests a "spy" inside the security forces tipped off the militants, el Sharef said.
US officials have not confirmed the account. They have spoken of an attack on the consulate's annex that killed two Americans, but said their report on the incident was still preliminary.
