After Friday’s deadly car-bombings in Nigeria’s capital, there can be no doubt that militants from the Niger delta retain a serious – even improved – capability to strike well beyond the uneasy oil region despite last year’s amnesty.

Even as the families of the seven dead begin to grieve, the government and oil groups will be worrying that the unprecedented strike in Abuja might herald a return to widespread assaults on the infrastructure of sub-Saharan Africa’s biggest oil and gas industry.

Tensions in the delta are certainly rising. Tit-for-tat attacks on rival political camps have hit Bayelsa, the home state of Goodluck Jonathan, the president and frontrunner for elections due by April.