Al-Qaeda’s core leadership in Pakistan may be losing strength, but the terrorist network’s affiliates in northern and central Africa are hardly weakening. In fact, U.S. officials say, the groups are increasingly collaborating with each other.

Three regional Islamic extremist groups – al-Qaeda in the Islamic Maghreb in North Africa, the Boko Haram in Nigeria and the al-Shabab militia in Somalia – are sharing trainers and copying each other’s tactics, according to Gen. Carter F. Ham, chief of the U.S. Africa Command.

“Just the fact that they want to connect is worrying,” Ham said at a breakfast hosted by the Defense Writers Group. While he said each of the three affiliates poses a threat locally, “what’s of greater concern actually is the voiced intent of the three organizations to more closely collaborate and synchronize their networks.”

As evidence he pointed to Boko Haram, a shadowy group in Nigeria believed responsible for carrying out a suicide attack on a United Nations headquarters in the capital of Abuja last month, killing 23 people. Al-Qaeda in the Islamic Maghreb, which is centered in Algeria, adopted suicide bombings as a tactic a few years ago and similarly attacked a U.N. complex in Algiers in December 2007.

Nigerian authorities have said that the alleged mastermind of the Abuja attack, Mamman Nur, has trained with al-Shabab fighters in Somalia.

Other U.S. counterterrorism officials agreed that the al-Qaeda affiliates in North Africa have been sharing trainers and tactics, but downplayed the possibility that they might merge operations extend their reach across the continent.

“Our assessment is that it’s just an exchange of trainers or training,” a senior U.S. defense official told reporters at a separate event Wednesday, speaking under condition of anonymity under ground rules set by the Pentagon. “They do make these temporary alliances of convenience…But I wouldn’t go down this legion of doom theory where they all end up holding lands.”

Ham, a four-star Army general who leads the Africa Command from its headquarters in Stuttgart, Germany, said each of the al-Qaeda affiliates has publicly threatened to attack Western targets and U.S. interests. Unlike al-Qaeda’s core command in Pakistan, however, he acknowledged that the African groups have not demonstrated an ability to attack the United States.

“I have questions about their capability to do so,” Ham said. “I have no question about their intent to do so.”

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