A radical Muslim cleric on Thursday rejected his nomination by Nigeria's president to a panel studying an amnesty offer to Islamist insurgents, saying he does not trust the government.

Datti Ahmed told reporters that Nigeria's government "is not sincere and will not honour any recommendations the amnesty committee will come up with."

He said the panel's report could be subject to tampering.

President Goodluck Jonathan on Wednesday announced the 26-member panel charged with looking at how amnesty should be offered to Boko Haram, an Islamist group blamed for killing thousands since 2009.

Jonathan had initially resisted the amnesty idea, but changed his position as pressure mounted, notably from leaders in the mainly Muslim north, the region hardest hit by insurgency.

Ahmed is a member of the radical Salafi branch of Islam and heads the Supreme Council of Sharia (Islamic law) in Nigeria, a group to which slain Boko Haram founder, Mohammed Yusuf, once belonged.

He was among several critics that Jonathan named to the panel, but it is not clear if his rejection of the offer will prove significant.

Shehu Sani, a prominent rights activist based in the north, rejected his own nomination late Wednesday, saying the authorities did not consult him before he was named.

It is unclear whether an amnesty offer would help reduce the violence, or whether members of the radical Islamist group are open to the proposal.

In an audio recording sent to AFP last week, Boko Haram's purported leader Abubakar Shekau, designated a global terrorist by the United States, rejected the idea.

The Boko Haram insurgency is estimated to have left more than 3,000 people dead since 2009, including killing by the security services.