Al-Qaeda indicated responsibility on Saturday for Tuesday’s attack on the US consulate in Benghazi, in which US Ambassador Chris Stevens and three other Americans were killed.

The terror group said the assault was executed in revenge for a US drone strike in June that killed the organization’s number two, Abu Yahya al-Libi. Libi was a Libyan national who served as lieutenant to Ayman al-Zawahiri, the head of al-Qaeda.

“The killing of Sheikh Abu Yahya only increased the enthusiasm and determination of the sons of (Libyan independence hero) Omar al-Mukhtar to take revenge upon those who attack our Prophet,” Al-Qaeda in the Arabian Peninsula said.

In a statement, the terror group urged more such attacks. “Whoever comes across America’s ambassadors or emissaries should follow the example of Omar al-Mukhtar’s descendants, who killed the American ambassador,”it said. “Let the step of kicking out the embassies be a step towards liberating Muslim countries from the American hegemony.”

Eastern Libya’s deputy interior minister, Wanis el-Sharef, said Friday that four people had been arrested in connection with the attack. Other reports Saturday said the Libyan authorities have identified 50 people involved in the attack.

In an audio recording released to coincide with the 9/11 anniversary, Zawahiri asserted an Islamic duty to “liberate” every inch of Muslim lands, and called upon Muslims to “purify” their countries of corrupt leaders during what he termed a period of “American weakness.” Muslims should “topple the western proxies” left in their countries “and especially the Saud clan and the gulf sheiks in the Arabian peninsula,” he declared.

US envoy Chris Stevens speaking to local media in Benghazi last year. (photo credit: AP/Ben Curtis)

US envoy Chris Stevens speaking to local media in Benghazi last year. (photo credit: AP/Ben Curtis)

As early as Wednesday, Israeli and American media reported that al-Qaeda operatives had carried out the attack, using the release of an anti-Islam movie that sparked violent protests around the Muslim world as a pretext for the chaos.

Killed in the attack in Benghazi were Stevens, information management officer Sean Smith, and private security guards Glen Doherty and Tyrone S. Woods.

Stevens died as he and a group of embassy employees went to the consulate to try to evacuate staff when the mob of protesters, including gunmen armed with machine guns and rocket-propelled grenades, attacked.

The consulate is a one-story villa located in a fenced garden in downtown Benghazi. A small contingent of Libyan security forces protecting the facility also fired in the air, trying to intimidate the attackers, said el-Sharef. But faced with the mob’s superior size and firepower, the Libyan security withdrew, el-Sharef said. Gunmen stormed the building, looted its contents and torched it, he said.

Al-Sharef said Stevens and a consulate staffer who had stayed behind in the building were killed in the initial attack on the consulate. The rest of the staff successfully evacuated to another building nearby, preparing to move to Benghazi Airport after daybreak to fly to the capital, Tripoli, he said. Hours after the storming of the consulate, a separate group of gunmen attacked the other building, opening fire on the more than 30 Americans and Libyans inside. Two more Americans were killed and 32 were wounded – 14 Americans and 18 Libyans, he said.

Stevens, he added, was visiting Benghazi to inaugurate an American culture center in the city. His body was identified by his Egyptian interpreter. Stevens died of severe asphyxiation from smoke inhalation, according to the Libyan doctor who tried for 90 minutes to save him. Ziad Abu Zeid said that Stevens was brought to the Benghazi Medical Center by Libyans the night before, with no other Americans, and that initially no one realized he was the ambassador. Stevens was practically dead when he arrived close to 1 a.m. on Wednesday. “We tried to revive him for an hour and a half but with no success,” Abu Zeid said.

Stevens was a career member of the US Foreign Service specializing in the Middle East, and served at various diplomatic posts around the region, including a stint as political section chief at the US consulate in Jerusalem.

He served as deputy chief of mission at the US Libyan embassy from 2007-2009, as part of the team that re-established US-Libyan official relations after a decades-long hiatus. During the Libyan civil war, he was the US representative to the Libyan Transitional National Council, and assumed his post as ambassador on May 22, 2012.