Last Updated Jan 10, 2014 3:12 PM EST
WASHINGTON -- The Obama administration for the first time on Friday identified two militant groups in Libya, including one led by a former Guantanamo Bay detainee, as being allegedly involved in the attack in Benghazi that killed Ambassador Chris Stevens and three other Americans.
The department designated the two branches of the Ansar al-Sharia in Libya, those in the cities of Derna and Benghazi, and a third branch in Tunisia as foreign terrorist organizations.
It also named Sufian bin Qumu, the leader of the Derna branch, and Ahmed Abu Khattala, a senior leader of the Benghazi branch, as specially designated global terrorists.
The Sept. 11, 2012 attack on the U.S. diplomatic mission in Benghazi is still a political issue in Washington. Republicans in Congress criticized the Obama administration's handling of the attack and the level of security at the diplomatic outpost.
U.S. officials have said that Khattala and an unspecified number of others have been named in a sealed complaint filed in U.S. District Court in Washington, but it's unclear what they have been charged with. No one has been arrested in the attack in which a group of militants set fire to the diplomatic mission and killed the four.
Qumu, who was released from Guantanamo Bay in 2007 and later freed in Libya, was described as a "probable member of al-Qaida" in an assessment written by officials at the military prison in Cuba in 2005. The assessment was released by Wikileaks.
The State Department, however, said al-Qaida did not orchestrate the Benghazi attack.
Spokeswoman Jen Psaki said the two Ansar al-Sharia branches are separate groups. "They're not official affiliates of core al-Qaida so we have no indications ... that core al-Qaida directed or planned the Benghazi attack," she said.
She also said the announcement was not an assertion that Ansar al-Sharia's branches in Benghazi and Derna were the only two organizations whose members were allegedly involved in the attack in Benghazi, that those groups pre-planned the attack well in advance or that they were somehow more responsible than any others involved.
She said officials were still investigating the Benghazi attack. "We're not designating them because of any new information to point to in terms of Benghazi and the events there," she said.
For more than two years, Libya has been held hostage to increasingly powerful militias. Initially they were formed out of rebel brigades that fought Libyan forces in the 2011 uprising. The government has relied on them to carry out security duties because of the weakness of the army, but they have carved out spheres of power of their own, and many are made up of Islamic extremists.
In addition to being involved in the attack on the U.S. mission and annex in Benghazi, the two branches of Ansar al-Sharia - created separately after the fall of dictator Moammar Gadhafi - have been involved in terrorist attacks against civilian targets, assassinations and attempted assassinations of security officials and political figures in eastern Libya. "Members of both organizations continue to pose a threat to U.S.," the State Department said in announcing the designations.
Last year, U.S. special forces carried out a raid in the Libyan capital of Tripoli to capture an al-Qaida leader linked to the 1998 American Embassy bombings in east Africa. The Pentagon identified the al-Qaida leader as Nazih Abdul-Hamed al-Ruqai, known by his alias Anas al-Libi. It is unclear whether U.S. forces have targeted Qumu or Khattala, who lives openly in Benghazi and has denied any role in the Benghazi attack.
Libya has been marked by unrest since Gadhafi's ouster. Armed groups that fought Gadhafi's army turned themselves into militias that exploited the weakness of the weak central government in Tripoli and operate independently of the police and the military.
Also designated was Seifallah Ben Hassine, founder of the group's branch in Tunisia that was involved in the Sept. 14, 2012 attack against the U.S. Embassy and American school in Tunis. The State Department said the attack put the lives of over 100 U.S. employees in the Embassy at risk.
"Ansar al-Sharia in Tunisia, which is ideologically aligned with al-Qaida and tied to its affiliates, including AQIM, represents the greatest threat to U.S. interests in Tunisia," the department said.
AQIM stands for Al-Qaida in the Islamic Maghreb, which is trying to undermine democratic transitions underway in North Africa.
The designations include various restrictions, including freezing their financial assets and barring U.S. individuals and companies from doing business or supporting or providing resources to them.
The department also issued a reward of up to $10 million for information leading to the arrest or conviction of anyone responsible for the Benghazi attacks.
Rep. Ed Royce, R-Calif., chairman of the House Foreign Affairs Committee, welcomed the designation, but said the administration has not done enough to track those responsible for the attack.
"Sixteen months after the terrorist attacks in Benghazi, the administration is confirming what it has long known - that Ansar al-Sharia carried out an attack against the United States that killed four Americans in Benghazi, Libya," Royce said in a statement. "The Obama administration should be doing all it can to hunt down those responsible for this terrorist attack. I'm gravely concerned that they are not."