Goodluck Jonathan, the Nigerian president, has sacked his defence minister and national security adviser after several months of violence in Africa’s most populous nation.

The decision was announced after Jonathan met his security team on Friday, hours after returning from a UN environmental summit in Brazil.

"The president has relieved the NSA [national security adviser Owoye Azazi] of his job and replaced him with Colonel Sambo Dasuki," Reuben Abati, presidency spokesman, said on Friday.

"The president has also sacked the minister of defence [Bello Mohammed] and will announce his replacement later."

He said the new security adviser would be Sambo Dasuki, a retired colonel, prominent northerner and cousin to the Sultan of Sokoto, Nigeria's highest Muslim spiritual figure.

It was not yet clear who would replace defence minister Mohammed.

Criticism has mounted over the government's response to the violence, with few public indications of what strategies are being employed beyond heavy-handed military raids to stop the onslaught of attacks.

Al Jazeera's Yvonne Ndege, reporting from Abuja, said the sacking of the defence chief may be seen as a bid to restore public confidence.

"There has been a real feeling that Nigeria's security apparatus, that means the military, police and state security forces, has not had a full grip on the violence, despite millions [in funding] being poured into it," our correspondent said.

"This move could be explained as a response to weeks of violence."

Sectarian violence

The fired national security adviser is a political ally of Jonathan's, with both men from Bayelsa state in the oil-producing south.

Azazi faced suspicion in the north, particularly after comments he made in April which many took as indicating that the violence was politically linked.

The spokesperson gave no reason for the move, but the two officials have been under fire for the mounting violence particularly in country’s north by the Boko Haram sect, which has claimed many attacks on churches in recent months.

It has emerged as a major security threat in Africa's top energy producer after it was blamed for a string of deadly attacks on government installations that has left hundreds dead.

Despite a state of emergency and a military crackdown on the Islamist sect, Boko Haram continued attacks on Christian worshippers, stoking a wider sectarian conflict and retaliatory attacks.

Several days of unrest in parts of northern Nigeria began on Sunday in Kaduna state, with suicide attacks at three churches that killed at least 16 people and sparked reprisals by Christian mobs, who burned mosques and killed dozens of Muslims.

The United States on Thursday said it had designated the head of the main branch of Boko Haram, Abubakar Shekau, a "global terrorist" along with two others tied to both Boko Haram and al-Qaeda's north African branch.

Source: Agencies