Western and Yemeni officials say one of the two brothers who carried out Wednesday's deadly attack on a French satirical newspaper trained with al-Qaida's branch in Yemen a few years ago.
American, European and Yemeni sources close to the investigation say Said Kouachi traveled to Yemen in 2011 to train with Al-Qaida in the Arabian Peninsula, or AQAP.
AQAP, formed in 2009 through a merger of the Saudi and Yemeni branches of al-Qaida, is one of the network's most active and lethal affiliates.
The group has carried out many attacks in an insurgency in Yemen, with the highest concentration in the southern part of the country. Most of the targets appear to be government facilities, with a particular focus on intelligence and security services.
At the same time, AQAP maintains a goal of striking Western targets and has orchestrated a series of high-profile attacks.
One of its most notable operations occurred in 2009 when the group dispatched a Nigerian-born man, Umar Farouk Abdulmutallab, who failed in trying to set off explosives sewn to his underwear aboard a commercial flight over the U.S. He thus became known as the "underwear bomber."
The following year, ASAP launched Inspire, an English online publication geared toward helping the group build its brand and spread its message of Jihad, or holy war. Many extremists motivated by radical interpretations of Islam have reportedly been influenced by the magazine and have used its bomb-making instructions.
One of the most notorious figures linked to AQAP was Anwar al-Awlaki, a U.S.-born cleric who by 2011 had become a senior figure in the group and its public face. He was killed in 2011 in a U.S. drone strike.
A senior Yemeni intelligence source told the Reuters new agency on Friday that Said Kouachi met with Awlaki when he trained in Yemen.
While the world was riveted this week on the tragic events unfolding in Paris, more than 30 people were killed in a car bomb explosion on Wednesday near a police college in the Yemeni capital, Sana'a.
AQAP has been suspected of carrying out the attack.