THE Woolwich killers are of Nigerian background, sources have confirmed.
But it is understood the men, who are being treated in separate hospitals while under arrest, are most likely to be British citizens converted to a radical form of Islam.
They are not thought to have links to terror groups based in Nigeria, such as the jihadist militant organisation Boko Haram.
The 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.
Religious groups and charities have come together to condemn the attack. The Muslim Council of Britain said the killers’ use of “Islamic slogans” indicated they were motivated by their faith.
A statement from the council said: “This is a truly barbaric act that has no basis in Islam and we condemn this unreservedly. Our thoughts are with the victim and his family.
“We understand the victim is a serving member of the Armed Forces. Muslims have long served in this country’s Armed Forces, proudly and with honour.
“This attack on a member of the Armed Forces is dishonourable, and no cause justifies this murder.”
The group called for vigilance and solidarity between “all our communities, Muslim and non-Muslim”, and for police to “calm tensions”.
Akbar Khan from Building Bridges said : “We totally condemn the killing of an innocent person in Woolwich.
“And we also condemn all forms of extremism wherever they are.
“The thoughts of the Muslim community are with the family of the man who lost his life, and we pray for him.”
Mohammed Shafiq from the Ramadhan Foundation said yesterday: “I wish to condemn the evil and barbaric crime carried out in Woolwich.
“Our immediate thoughts are with the family and friends of the victims. From whatever angle you see the attack, it was at every level evil.
“We must allow the police to gather all the facts before unnecessary speculation and wait for the facts before determining its impact on our country.
“But what happens in the days to come, London and our nation will come together and will not be divided. The terrorists will never win and succeed in their evil plans.
“But tonight we think of the family of that soldier killed.”
Fiyaz Mughal, the director of charity Faith Matters, said: “The cold-blooded killing of a serving British soldier is a crime that sickens every member of every community in the UK.
“For the peace of our communities to be shattered like this is almost unthinkable. We must come together, isolate those who believe that extremism and violence are acceptable, and work to ensure that they meet the full force of the law.
“We must send a clear message to anyone that an attack on a serving soldier going about their daily activities is something that must be utterly condemned.”
Former home secretary Lord Reid condemned the “brutal, inhumane and terrible murder of an innocent person”.
While he said the threat from terrorists was continual, he insisted they would not succeed in their bid to “impose their will on others” in the UK.
Lord Reid told BBC Radio Scotland’s Good Morning Scotland the killing in Woolwich was a “horrific and terrible attack”, and added: “The bad news is that becomes harder to prevent.”
He said it was “a testament to the effectiveness of our security forces in this country that they have prevented it for many, many years”.
The former home secretary added: “We can get complacent - its easy to think because there hasn’t been a terrorist attack in the recent past that somehow the threat has gone away. I have continually said it hasn’t, it’s there continually, it’s still substantial.
“The macabre manner of the killing and the propaganda associated with it was meant to terrify and frighten people, because that is the nature of what terrorists do - which is to try to impose their will on others, through fear and indiscriminate violence.
“But it won’t work. It never has in the past in this country and it won’t in the future.”
Julie Siddiqi, of the Islamic Society of Britain, told the BBC Radio 4 Today programme: “We can’t allow the voices of Nick Griffin and the far right to become louder than ours in the coming days. They will say what we have to say and it gives us even more incentive to speak out and come together and not allow people like that to divide us as a country.
“The people who did this act yesterday do not speak in my name, do not speak for my community or the rest of the country. We have to come out with the strongest condemnation, which is what I’m seeing this morning.
“All of the Muslim organisations have come out with the strongest possible terms to say there is absolutely no excuse whatsoever, no justification for anything like this.
“This is one of the most shocking things I have seen in recent years and to have the people of Woolwich have to experience that so close to them, I just feel is absolutely horrific.”