A Nigerian minister tasked with talking to Boko Haram claimed Wednesday that he was in ceasefire negotiations with the Islamist insurgents, but doubts persisted that a peace pact could be secured.

There have been previous claims of peace talks between the government and the militants, but the negotiations, if they did indeed occur, failed to quell the violence.

Nigeria's government and military have regularly been accused of spreading false information regarding the insurgency.

The fresh claim of ceasefire talks came as the Muslim holy month of Ramadan began.

It also follows an attack on a secondary school in the northeast on Saturday by alleged Boko Haram members that left 42 people dead, almost all of them students.

Kabiru Tanimu Turaki, a cabinet minister and chair of a presidential panel tasked with exploring an amnesty offer for insurgents, told journalists he was dealing with credible Boko Haram members, authorised to negotiate by insurgent leader Abubakar Shekau.

"We have been speaking to the proper people," Turaki said after a cabinet meeting in the capital Abuja.

Reports of the alleged talks emerged Monday when Turaki told Radio France International's Hausa language service that Boko Haram had "agreed to lay down arms".

On Wednesday, he said the two sides "are still working on the framework" of a ceasefire.

Defence spokesman Brigadier General Chris Olukolade was not available to comment, but he was quoted Wednesday in This Day newspaper as saying the military was "not aware of any ceasefire".

Turaki claimed to be negotiating with "somebody who is second-in-command as far as Boko Haram is concerned".

"He has been discussing with us with the full knowledge and authority of Imam Abubakar Shekau...We have done checks on him."

The man has been identified as Mohammed Marwan. He told RFI that Boko Haram was "asking for forgiveness from the society for people killed".

In his video messages, Shekau has never voiced contrition, but instead showed defiance while insisting the group's killings were justified. He has also warned against imposters seeking to represent the group.

A professor at the northern Ahmadu Bello University who has closely followed the Boko Haram insurgency, Abubakar Siddique Mohammed, told AFP he has doubts that a ceasefire is realistic.

"I don't know who they are talking to...They need to show that the man they are discussing with actually represents Shekau," he said.

Boko Haram has said it is fighting to create an Islamic state in Nigeria's mainly Muslim north as part of its insurgency that has left 3,600 people dead, including killings by the security forces.

A sweeping military offensive launched in Nigeria's northeast in mid-May has been seeking to end the four-year insurgency, but the violence has continued.

Nigeria has released women and children held in connection with the insurgency as a peace gesture amid the offensive.