Nigeria claimed to have reached a deal with the Boko Haram rebel group on a ceasefire and the release of more than 200 kidnapped schoolgirls but doubts immediately surrounded the purported breakthrough.

Chief of Defence Staff Air Marshal Alex Badeh on Friday told senior military officials from Nigeria and Cameroon meeting in Abuja that a "ceasefire agreement" had been concluded between the government and the rebels.

"I have accordingly directed the service chiefs to ensure immediate compliance with this development," he added.

Badeh's announcement came after a senior aide to President Goodluck Jonathan, Hassan Tukur, told AFP news agency an agreement to end hostilities had been reached following talks, as well as for the release of 219 girls held captive since April.

However, sources told Al Jazeera that substantial progress had been reached in negotiations about the abducted girls but that no definite deal had been agreed.

A precedent of previous government and military claims about an end to the deadly five-year conflict and the fate of the missing teenagers left many observers cautious.

Jonathan is expected to declare his bid for re-election in the coming weeks, and positive news about the hostages and the violence would likely give him a political boost.

Shehu Sani, a Boko Haram expert who has negotiated with the group on behalf of the government said had "never heard" of Danladi Ahmadu, whom Tukur claimed represented the rebels at talks.

Ralph Bello-Fadile an advisor to Nigeria's National Security Advisor (NSA), said the NSA has been inundated with fraudsters claiming to represent Boko Haram leader Abubakar Shekau.

"Government wants to negotiate but so far nobody has come forward who speaks for Shekau," he told a Chatham House conference in Abuja on Monday.

The Nigerian government's own security spokesman, Mike Omeri, also said that no deal had yet been reached on releasing the girls.

The United States said it could not confirm whether a deal had taken place.

"Obviously, we would welcome an end to hostilities, a restoration of security and, I think it should go without saying, would welcome the release of those girls that have been gone far too long. But we cannot independently confirm that at this point," said State Department spokeswoman Marie Harf.

"This ceasefire is incredibly promising, but we aren't there yet - until every girl is released negotiations must continue," added Hussaini Abdu, the country director for ActionAid Nigeria.

Chad talks

Tukur said he represented the government at two meetings with the rebels in Chad, which were mediated by the country's President Idriss Deby.

"Boko Haram issued the ceasefire as a result of the discussions we have been having with them," said Tukur, adding that Ahmadu made the announcement on Thursday evening.

"They have agreed to release the Chibok girls," he continued, referring to the girls seized in northeast Nigeria on April 14, causing global outrage.

Leaders of the Bring Back Our Girls campaign, which has been pressuring the government to act, gave a cautious welcome to a possible release.

"We are monitoring the news with huge expectations," they said on Twitter.

Ndjamena refused to comment but security sources in the country said Chad, which Jonathan visited for talks with Deby early last month, had been involved in the discussions.

The source also said a ceasefire agreement was reached as well as the release of 27 hostages, 10 of them Chinese nationals, who were kidnapped in northern Cameroon earlier this year.

The release of the hostages last weekend was "a first strong signal" from Boko Haram to prove their good faith, the source added but did not mention the schoolgirls.

Cameroon announced on Friday that eight of its soldiers and 107 Boko Haram fighters were killed during fierce fighting in its far north region on Wednesday and Thursday.

In Nigeria, unidentified gunmen on Friday killed eight people on a road near Shaffa village in Borno state, two local residents said, but it was not clear if the attack was by the rebels.

The incident, however, happened near where a prominent Muslim leader, the Emir of Gwoza, was killed by Boko Haram militants in May.

Discrepancies

Ahmadu gave an interview broadcast on Friday on the Hausa language service of Voice of America radio in which he claimed to be the group's "chief security officer" and in charge of publicity.

He made no mention of an end to hostilities and was vague on details of the apparent talks, even claiming not to have met Shekau.

He also referred to the jihadi group as Boko Haram, a name that means 'Western education is forbidden' which was imposed on the Islamist radicals by outsiders. The insurgents themselves never use the term.

The group's known leaders have exclusively used the name Jama'atu Ahlis Sunna Lidda'awati wal-Jihad, which means "People Committed to the Propagation of the Prophet's Teachings and Jihad".

He made no reference to the Chibok girls and did not list the creation of an Islamic state in Nigeria's mainly Muslim north - the core, unwavering Boko Haram demand since the uprising began.