Some counterterrorism experts believe that Droukdel suspected Belmoktar of a role in the Benghazi attack and was anxious that such a high-profile operation would promote a severe backlash from the United States, setting back AQIM's efforts to establish a foothold in Mali and Libya.

Belmoktar was one of several leading militants based in Mali who spent time in Libya in the aftermath of Moammar Gadhafi's overthrow, developing relationships with militant Islamist brigades and buying weapons with the proceeds of smuggling and kidnapping operations.

According to sources in direct contact with Western intelligence agencies, Belmoktar was in Libya for four months from December 2011. They say his visit was facilitated by the leader of a radical Islamist militia with influence in Benghazi and the East.

According to the sources, he met a Libyan veteran of jihad in Afghanistan who had set up camps near Sabha in southern Libya providing training for jihadists from Algeria, Morocco, Mauritania and Mali as well as Libyans and ethnic Tuaregs. Western intelligence officials believe the camps may have been used by those who attacked the In Amenas gas facility in January, according to the sources.

Across North Africa and as far east as Syria, counterterrorism agencies are seeing a fluid movement of fighters, weapons and expertise among jihadist groups.

The New York Times reported in January that several of the militants involved in the Algerian attack had also been in Benghazi in September, citing a senior Algerian official. The official said one of the militants captured had described the Egyptians' role in both assaults, according to the Times.

Asked about the report at a hearing of the Senate Foreign Relations Committee on Jan. 23, then-U.S. Secretary of State Hillary Clinton said: "I cannot confirm it. I can give you the background that I was able to obtain. This information is coming from the Algerian government related to their questioning of certain of the terrorists that they took alive."

She also alluded to links between the attack in Algeria and sources of weapons in Libya.

"The Pandora's box of weapons coming out of these countries in the Middle East and North Africa is the source of one of our biggest threats. There is no doubt that the Algerian terrorists had weapons from Libya. ... So we just have to do a much better job," she said.

The combination of different jihadist groups and factions, in shifting coalitions of the willing, has become a growing feature of the militant landscape, and one that makes tracking individuals and groups more difficult. Instability in North Africa -- especially in Libya and Mali -- has afforded these groups new space in which to operate.