BENGHAZI, Libya -- A Libyan security guard who said he was at the U.S. consulate here when it was attacked Tuesday night has provided new evidence that the assault on the compound that left four Americans dead, including the U.S. ambassador to Libya, was a planned attack by armed Islamists and not the outgrowth of a protest over an online video that mocks Islam and its founder, the Prophet Muhammad.

The guard, interviewed Thursday in the hospital where he is being treated for five shrapnel wounds in one leg and two bullet wounds in the other, said that the consulate area was quiet – “there wasn’t a single ant outside,” he said – until about 9:35 p.m., when as many as 125 armed men descended on the compound from all directions.

The men lobbed grenades into the compound, wounding the guard and knocking him to the ground, then stormed through the facility’s main gate, shouting “God is great” and moving to one of the many villas that make up the consulate compound. He said there had been no warning that an attack was imminent.

“Wouldn’t you expect if there were protesters outside that the Americans would leave?” the guard said.

The guard, located by searching hospitals for people injured Tuesday night, said he was 27 years old but declined to give his name. He asked that the hospital where he is being treated not be identified for fear that militants would track him down and kill him. He said he was able to escape by telling one of the attackers that he was only a gardener at the compound. The attacker took him to the hospital, the guard said.

Libyan authorities told reporters Thursday that they had made four arrests in connection with the consulate assault, but they cautioned that leaders of the group blamed for the attack, an Islamist organization known as Ansar al Shariah, denied that they had given the order to attack. But the guard’s tale suggested that whoever ordered the assault had been able to call upon a large number of people to carry out what appeared to be an organized attack.

Wanis al Sharif, the deputy interior minister responsible for Libya’s eastern region, which includes Benghazi, told a group of local reporters that in addition to the four people under arrest, authorities were monitoring others for possible involvement in the attack.

“There is a group under our control, and there is another we are monitoring,” Sharif said.

Sharif said that Ansar al Shariah’s leaders had suggested that those carrying the group’s flag during the assault were rogue members acting on their own.

“They called me and told me you have wronged us,” Sharif said. “They told me that there may be individual acts.”

Ansar al Shariah – Partisans of Islamic law – which is based in Benghazi, is one of the largest Islamic extremist groups now operating in Libya, according to an analysis published Wednesday by Aaron Zelin of the Washington Institute for Near East Policy.

The shadowy organization is led by Muhammad Zahawi and maintains "online connections" to a similarly named group in Tunisia. A unit, or katiba, based in Derna, an eastern town from which extremists made their way to fight U.S. forces in Iraq, is commanded by a former Guantanamo prison detainee, Abu Sufayan bin Qumu, according to Zelin.

Where Sharif’s findings would fit in the U.S. investigation into the death of Ambassador Christopher Stevens and the other Americans remained unclear. But the guard’s tale suggests that there were many more than four people involved in the attack.