The cleric has since been joined by a former aide to one of the group's founders. Neither man has been named, possibly for their own safety. While the Nigerian government has insisted that it is not willing to enter prisoner swap negotiations, the source claimed that dialogue had been going on in secret for several days.
"Contrary to the public rejection of any swap deal by the Nigerian government, there are some on-the-ground talks taking place," the source said. "An agreement was reached about two or three days ago in principle to start releasing some prisoners."
He said that among the prisoners that the group wanted released would be wives and families of Boko Haram fighters, some of whom have been taken into custody by the Nigerian government in order to exert emotional pressure on the fighters. "The group also has a list of lower-level fighters that it wants released as well, but they are not high-profile ones," the source added.
Young French demonstrators hold up papers with the names symbolising the abducted girls in Nigeria during a demonstration at Trocadero, in Paris. Photo / AP
He said that in exchange, Boko Haram was willing to start a "gradual" release of about 100 of the girls - possibly beginning as early as the coming week. "Depending on how the other side responds, the girls will be released in small groups. They will be left at a certain safe location and the authorities will then be told as to where they can pick them up from."
A spokesman for the Nigerian government declined to comment on the claims that it was in negotiations, saying: "There are all kinds of claims about efforts at negotiations, some of them being floated around in the media, but we do not think the media is the right place for us to have this discussion."
Details of Boko Haram's offer emerged as officials investigated reports that it was responsible for the kidnapping of up to 10 Chinese workers in neighbouring Cameroon, where the group now also has a presence. On Saturday, Nigeria and its neighbours, including Cameroon, Benin, Chad, and Niger, declared "war" on Boko Haram after an international summit in Paris hosted by Francois Hollande, the French president.
The offensive will involve coordination of surveillance efforts aimed at finding the girls, the sharing of intelligence, the tightening of border controls, and a regional counter-terrorism strategy with Western help. The Daily Telegraph source said Boko Haram leaders had been upset by the declaration of "war" at the Paris summit, and that this could encourage it to withdraw its offer.
Video: Extremist video shows abducted girls praying
At the summit, the countries agreed to forge a regional counter-terrorism strategy with expertise and training support from Britain, France, the European Union and the United States.
The countries also agreed to push for UN sanctions against the leaders of Boko Haram and another Nigerian Islamist group, Ansaru. America has already designated the leaders of both as terrorists. Britain will host a follow-up meeting to discuss the crisis next month. It is thought that the kidnapped schoolgirls are being held somewhere in north-east Nigeria or across the border in Cameroon.
Boko Haram's leader, Abubakar Shekau, demanded the release of his "brethren" in a video last week in which the kidnapped schoolgirls were paraded.
The Chinese embassy in Cameroon confirmed that 10 of its workers had disappeared on Friday at a site near the town of Waza, 12 miles from the Nigerian border and close to the Sambisa forest, a Boko Haram stronghold.
Ten vehicles belonging to Sinohydro, China's state-run construction company, which is repairing roads in Cameroon, were also taken following a five-hour gunfight. A Cameroon special forces soldier was reportedly killed.
