It is understood that the team – drawn from Whitehall departments including defence, international development and the Foreign Office – may include military officers but will concentrate on planning, co-ordination and advice to local authorities, rather than operations on the ground to free the girls.
Nigerian President Goodluck Jonathan accepted the UK offer of help in a phone call with David Cameron, shortly after the Prime Minister told the House of Commons that the mass abduction was “an act of pure evil”.
Mr Cameron’s official spokesman said the UK team will fly to the west African state “as soon as possible,” but was unable to say how large the group will be.
Mr Cameron’s spokesman rejected suggestions that the UK had been slow to provide assistance following the abduction, which happened on 15 April.
“We have been in close contact from the outset with the Nigerian government on this issue,” said the spokesman.
“The Foreign Secretary spoke to his Nigerian counterpart days after the incident in mid-April. We have been in regular contact through the Foreign Office and High Commission at all stages, making clear that an offer of assistance that the Nigerian government would find helpful was there.”
Downing Street said Mr Cameron and Mr Jonathan agreed to “explore how to further strengthen co-operation on counter-terrorism in the longer term, to help in the prevention of such attacks in the future”.
Mr Cameron’s spokesman added: “The Prime Minister and president very much agreed about the importance of the international community continuing to work together to meet the challenge posed by Islamist extremism and violence.”
Britain already has a small military training team in Nigeria, assisting the African country in its response to the extremist groups behind a five-year Islamist uprising which has killed thousands.
The announcement of the new assistance came as reports emerged of an attack on the north-eastern border town of Gamboru Ngala by Islamist militants, which cost the lives of as many as 300 people.
Mr Cameron told the Commons: “We should be clear this is not just a Nigerian issue - it is a global issue. There are extreme Islamists around our world who are against education, against progress, against equality, and we must fight them and take them on wherever they are.”
President Barack Obama has said the US will do “everything we can” to help Nigeria find the missing girls, adding: “We’re also going to have to deal with the broader problem of organisations like this, that can cause such havoc in people’s day-to-day lives.”
The US team will include military and law-enforcement personnel skilled in intelligence, investigations, hostage negotiation, information-sharing and victim assistance, as well as officials with expertise in other areas, said the White House.
But spokesman Jay Carney said the US was not considering sending armed forces.
The Nigerian police have offered a £176,000 reward for information leading to the rescue of the girls.