In the desert borderlands of Mali and Niger, UN envoys have been seized and one tourist executed by a group calling itself al-Qa'ida in the Maghreb, the same organisation that is waging a bombing campaign in Algeria.

In Nigeria, Flight 253 terror suspect Umar Farouk Abdulmutallab's homeland, 500 people died earlier this year in bloody battles between authorities and an Islamic sect billed as the "Nigerian Taliban". And three men from Mali appeared at a New York courthouse earlier this month described as the first al-Qa'ida operatives to be charged with drug trafficking through the Sahara. US authorities intend to prove that terrorists have formed a growing alliance with the drug lords that run the narco-states of West Africa.

On the other side of the continent in Somalia, previously unheard of suicide bombings have become commonplace. Islamic militants al-Shabaab have had their ranks swollen by foreign jihadists and post pictures of their deadly attacks as tributes to Osama bin Laden. Diaspora Somalis are coming under huge scrutiny after one man was connected with a bomb plot in Australia, while US and European-raised Somalis have returned to their homeland as volunteer suicide bombers. The UN last week announced sanctions against Eritrea for alleged assistance to an al-Qa'ida-linked movement, amid fears that the Western-backed Somali government could fall, clearing the way for the terror network to take charge.

Born in Africa, or at least incubated in Sudan, al-Qa'ida is said by some to be leading a radicalisation of the continent's huge Muslim population. In testimony to the US Senate in March, the head of US Africa Command, General William Ward, said al-Qa'ida had increased its influence "dramatically" across northern and eastern Africa over the past three years.

There is, however, no uniform, radical wave sweeping the continent. Al-Qa'ida isn't a mass movement in Africa in any recognisable form.

The conflicts, tensions and crises that lie beneath these events are differentiated and almost always local in their genesis. The struggles and objectives have not been global and the clearest unifying factor is the emergence of radical Islam in anarchic, failed states from East to West Africa.

There is a clear pattern: first the act is committed, then allegiance to al-Qa'ida is claimed – just as was the case with Abdulmutallab, arrested at the weekend for the attempted bombing of the Detroit-bound airliner.

The terror network has long been suspected of having a core operation which takes its orders from Bin Laden and senior figures such as the Egyptian Ayman al-Zawahiri, and a looser group of affiliates whose aims – sometimes only temporarily – overlap with the core al-Qa'ida. The second autonomous set can be said to operate in something akin to a franchise system.

Al-Qa'ida in the Maghreb only began using this name in early 2007. Prior to its rebranding the group was a nationalist Islamic insurgency fighting the Algerian government in a left over clash from the vicious civil war there. The GSPC, as it was previously known, was itself a splinter of the feared Armed Islamic Group, or GIA, which refused to lay down arms after a 1999 amnesty. The new group labelled itself "fundamentalist", but by the end of 2006 it was running out of fighters and weapons. The alignment with Bin Laden's network has prompted a resurgence.

In Nigeria the search for links to al-Qa'ida has turned up nothing. Boko Haram, the northern Nigerian sect that emerged bloodily in July after members were arrested for allegedly plotting to attack police stations, was defiantly local.

Its leader Mohammed Yusuf, who was executed during the clashes, was radically opposed to Western education and wanted sharia law to be adopted across Nigeria.

Based in Maiduguri, capital of the north-eastern state of Borno, his followers include former university lecturers and students in other northern states, as well as illiterate, jobless youths. Their name, meaning "Western education is sinful", won comparisons with the Taliban.

In the case of Somalia the foreign template of Afghanistan has weighed heavily on the Horn of Africa nation, with some analysts arguing that clumsy US-led interventions aimed at smashing networks connected to al-Qa'ida have served to foster the connections they were meant to prevent.

And now in the case of the Nigerian would-be bomber, the real radicalisation may have come from the more conventional quarter of Yemen and not Africa at all.