Since the global campaign on social media to raise awarenessof the schoolgirls' plight - #BringBackOurGirls - Western nations have pledged assistance to Nigeria. On Tuesday, the United States revealed that it was flying surveillance aircraft and sharing satellite photos with the Nigerian government.

A group of advisers from the FBI, defence, and state departments have also been sent to Nigeria to assist in the search for the girls. The UK government has also sent a team of experts, as has France and China.

Some, including the US Senator John McCain and the Conservative MEP Daniel Hannan, have advocated sending soldiers or special forces to rescue the schoolgirls. Archbishop Welby said, however, that, while it was right to offer advice and support, military action would be extremely difficult.

"We need to offer help humbly and respectfully to a people of suffering in a country of great talent and potential. Above all, we are called to identify with the poor and suffering in prayer."

Before his present appointment, Archbishop Welby travelled to Nigeria on several occasions to help reconciliation efforts with various groups, including precursors of Boko Haram. Speaking to Radio 4 on Sunday, he also said that even though Boko Haram was a disparate and "irrational" group, the Nigerian authorities should try to negotiate with them.

"[Boko Haram] are very difficult to deal with and utterly merciless. [They] have a very difficult inner core and negotiation there is extremely complicated, though I think you need to try."

On Monday, Boko Haram released a video showing 136 of the girls, dressed in hijabs, and offered to exchange the girls for captured Boko Haram fighters in prison. The group claimed that the girls, who were mostly Christians, had converted to Islam.

In the video, the leader of Boko Haram, Abubakar Shekau, said: "I swear to almighty Allah, you will not see them again until you release our brothers that you have captured." Mr Shekau had threatened to sell the girls into slavery in a previous video last week.

The response from the Nigerian authorities has been confused. The the interior minister rejected any prisoner exchange, while a government statement suggested that all options remained available.

Archbishop Welby said on Sunday that the Anglican Church in Nigeria had been working for years to counteract the violence of Boko Haram. "Archbishop Okoh and his bishops have worked very well, though great suffering and sacrifice of life, to work with Muslim groups that are seeking reconciliation. The vast majority of the population are not involved with Boko Haram, but are terrorised by them."

Primates around the Anglican Communion have also spoken out against the kidnapping, including those of Southern Africa, Brazil, and Canada. The Presiding Bishop of the Episcopal Church in the United States, Dr Katharine Jefferts Schori, said in a statement that the Church was horrified that those who should be addressing the crisis were "look[ing] the other way".

"I pray that all Episcopalians, and all people of faith and good will, will pray and plead with their political leaders to find the kidnappers, liberate these girls, and restore them to the safety they deserve."

As the global spotlight on Boko Haram intensified, clashes between Muslim and Christian communities in Nigeria continued. The advocacy group Christian Solidarity Worldwide (CSW) reported on Monday that violence had broken out in southern Kaduna state, in the north-west of Nigeria.

A dispute between Muslim and Christian youths had led to the demolition of a church; and then two mosques had been burnt down in retaliation, CSW said. The predominantly Christian area had suffered violent attacks since 2011, and some felt that the security forces did not provide adequate protection.

'External intervention is always difficult'

Justin Welby sets out the challenges that are presented in tackling Boko Haram

BOKO HARAM was established in north-eastern Nigeria in the first years of this century. Called by a variety of names, it formed cells in different parts of the north-east, and carried out progressively more serious terrorist attacks mainly in the northern part of Nigeria, with the highest intensity in Borno state and the next-door states of Yobe and Adamawa. There were also major attacks in Kano, Kaduna, Jos, Abuja, and other places.

I spent a certain amount of time in these areas between 2005 and 2011. Groups have, at various times, fled the perceived (by them) corruption of the cities, and set up communities in the Bush. From time to time they clash with police or others, and they are easily radicalised.

On one occasion I met with one of these communities for a day's discussion, sitting on the floor of the mosque, talking about politics, theology, and how to lead a good life. High-technology IT, very conservative attitudes to women and to education, as well as a fear of outsiders, combine to create a potent mix, easily dominated by a charismatic leader.

Boko Haram's stated aim is to establish a radical and extremist Islamic caliphate in northern Nigeria. The Caliphate would next be extended to the rest of Nigeria, and beyond. Well-armed and funded, they have attacked Christians and their churches, as well as Muslims and mosques where they have encountered opposition. A number of Anglican dioceses have been especially severely affected.

They have also targeted government institutions - especially the police. There is the belief by many, including President Goodluck Jonathan, that members of the group exist in various parts of the Nigerian society, including the armed forces.

THE latest abduction of more than 200 schoolgirls, who were in the middle of their examinations, has rightly earned robust international condemnation, including by several Primates of the Anglican Communion. The Church of Nigeria is intimately involved, through interfaith dialogue and other efforts, in seeking a solution.

Any approach to tackling the problem will have to combine police action, "hearts and minds" approaches to convince local populations that it is possible to oppose Boko Haram, and careful spiritual and economic development. It will take a long time. The area is vast, with poor communications.

The sources for the impact of Boko Haram are economic, historical, religious, and ethnic. Youth unemployment affects the majority of young people in the north-east. Power is erratic, industry is declining, and agriculture is poor, besides being affected by southward expansion of the Sahara. There is a perceived lack of good development, and much corruption.

EXTERNAL intervention is always difficult. In the first place, Britain's history as the colonial power, and the role of the United States of America in Iraq and Afghanistan, makes both countries (and indeed much of the "Christian West") suspicious for many Muslims. In the period after 9/11, a huge proportion of children in some areas were named "Osama" in support of Bin Laden.

In the fighting of recent years, the Nigerian Army has been put under very severe pressure, and there have been reports by international agencies (always strongly denied) of human-rights abuses.

External help should involve advice where it can be offered, support for those who are displaced, expertise in training and development, and, above all, support for reconciliation, which will be long and difficult.

The crisis has claimed many lives. We need to offer help humbly and respectfully to a people suffering in a country of great talent and potential. Above all, we are called to identify with the poor and suffering in prayer - and then to act as God calls us to be the answer to the prayer we pray.

END