JOHANNESBURG — The Westgate Mall attack in Kenya threw the spotlight on al-Shabab, a Somalia-based group of Islamic militants that claimed responsibility. But its relationship with al-Hijra, a relatively obscure cell of extremists in Kenya, represents what terrorism analysts say is a worrying trend in Africa: an increase in collaboration among religious radicals across borders and vast, poorly policed regions.
For now, the experts say, this networking lets militant groups in Africa aid one another in the face of pressure from security forces, but doesn't entail a coordinated, continent-wide strategy that could sideline the local agendas they hold dear. The fear is that the more these groups talk to each other, the more people they will kill as they thwart efforts to contain them.
"It is the growing connectivity between some of these groups that is starting to form a network across Africa which could be very, very dangerous," Gen. Carter Ham, then chief of the U.S. military's Africa Command, said in December. Ham, who has since retired, warned at the time that al-Shabab and other like-minded outfits were increasingly working together in the fields of training, funding and weapons.
No evidence has yet emerged that shows such regional networking played a role in the Sept. 21 Nairobi mall attack that killed at least 67 people. But some observers believe al-Hijra may have played a role in the mall attack, noting its close ties to Somali militants.
"It is really a close affiliate, a Kenyan part of al-Shabab," said Stig Jarle Hansen, a Norwegian academic who has written a book about al-Shabab.
Al-Shabab, which has pledged allegiance to al-Qaida, said the assault was payback for Kenya's military role in pushing back Islamic fighters in neighboring Somalia. The Kenyan police, meanwhile, may be going after suspected al-Hijra members at home.
Al-Hijra, formerly known as the Muslim Youth Center, has been "plagued by unexplained killings, disappearances, continuous 'catch and release' arrest raids and operational disruptions," the United Nations said in a July report on Somalia and Eritrea.
Human rights groups blame Kenyan police for the forced disappearances and executions.
"Al-Hijra is striving to regain the initiative, in part through its fighters in Somalia returning to conduct new and more complex operations and through strengthening its ties to other groups in the region," the U.N. report said. It said al-Hijra was building links with extremists in Tanzania, as well as al-Shabab affiliates in Rwanda and Burundi.
These links among Islamic militants in Africa pose new challenges for resource-poor governments that sometimes struggle to work together, even as radical fighters get cash from smuggling and other illegal activities.
Many Islamic militants involved in deadly attacks in Africa find common cause with al-Qaida, adopting its hardline Islamic ideology and anti-Western agenda and benefiting from its global propaganda networks.
"There are definitely linkages between the groups," said Hussein Solomon, a senior professor in political studies and governance at the University of the Free State in South Africa and author of "Jihad: A South Africa Perspective."
The ideology "is the glue which binds them all and which gives them a transnational nature," he said. But those binds can fray.
"Sometimes these alliances are somewhat short-lived because of the tensions between local and more global aspirations," said Bill Braniff, executive director of START, a terrorism research center based at the University of Maryland in the United States.
Other key groups are al-Qaida in the Islamic Maghreb, in north and west Africa; Nigeria's Boko Haram, blamed for mass killings of civilians in the past week; and al-Qaida in the Arabian Peninsula, based in Yemen, across the Gulf of Aden from Somalia.
Boko Haram sometimes uses tactics and language reminiscent of al-Qaida, but it remains fiercely focused on a local agenda, railing against what it calls Nigerian state oppression and corruption and seeking implantation of a harsh version of Islamic law, or Shariah, in all of Africa's most populous country.
Valentina Soria, a security analyst and al-Shabab expert with London-based IHS Jane's, said there does not appear to be a "coordinated strategy" and that collaboration consists of "operational connections."
In a report last year, Soria said some groups were using more suicide bombers and adopting a "strategy of 'spectacle'" in attacks that seemed modeled on al-Qaida's style. The use of Twitter by purported al-Shabab militants during the Kenya mall attack fits the al-Qaida profile of aggressively using the media as a tool to promote its message.
Al-Shabab is believed to have undergone a deadly power struggle within its ranks, and analysts have speculated that the targeting of the Westgate Mall, popular among foreigners, means the leadership is intent on spectacular attacks with international impact.
Braniff noted "increasing lethality of groups on the periphery of al-Qaida." According to U.S. State Department figures, Somalia and Nigeria were among the top 10 countries with the most terrorist attacks in the world in 2012.