The Woolwich killers are of Nigerian background, sources have confirmed, but it is understood they are most likely to be British citizens converted to a radical form of Islam.
The men, who are being treated in separate hospitals while under arrest, are not thought to have links to terror groups based in Nigeria, such as the jihadist militant organisation Boko Haram.
The British Foreign Office warns of a high threat from terrorism in the West African nation and raises the prospect of a risk of retaliatory attacks following the French intervention in Mali.
Boko Haram is the most prominent terrorist threat in Nigeria. The group’s extremists aspire to establish Islamic law in Nigeria and carry out attacks across states mainly in the north.
In 2011, Boko Haram claimed responsibility for the bombing of the UN building in the Nigerian capital of Abuja, which killed 23 people in an act that showed the group could target Western interests.
The group, whose name means ”Western education is sacrilege”, was blamed for nearly 800 killings last year alone.