ABUJA: Nigeria's top Muslim spiritual leader sought to calm tensions Tuesday after meeting the country's president over deadly Christmas attacks claimed by Islamists that risk inflaming sectarian divisions.

The meeting came as a Christian leader in the country's north warned the government must take action to address spiralling violence or risk religious war, though he stressed Christians must not retaliate.

The US military commander for Africa meanwhile expressed renewed concern over Nigerian Islamist sect Boko Haram, which claimed the Christmas attacks, particularly over suspicions of links with foreign groups like Al-Qaeda.

Nigeria's top Muslim leader said after a 90-minute meeting with President Goodluck Jonathan that the attacks which killed 40 people, including worshippers leaving a Catholic church near the capital, did not signal a religious conflict.

“I want to assure all Nigerians that there is no conflict between Muslims and Christians, between Islam and Christianity,” Sultan of Sokoto Muhammad Sa'ad Abubakar told journalists.

“It's a conflict between evil people and good people. The good people are more than the evil ones, so the good people must come together to defeat the evil ones, and that is the message.” Jonathan did not speak publicly after the meeting, but his national security adviser urged Christians not to retaliate over the Christmas bombings.

“We are Nigerians. I don't see any major conflict between the Christian community and Muslim community,” Owoye Azazi said.

“Retaliation is not the answer, because if you retaliate, at what point will it end? Nigeria must survive as a nation.”Nigeria has seen scores of attacks claimed by Boko Haram, but some analysts said the Christmas bombings marked a dangerous escalation in a country divided between a mainly Muslim north and predominantly Christian south.

The head of the northern chapter of Nigeria's main Christian organisation warned that the government must address the problem to prevent “religious war.” He said Christians were frightened and security was being tightened at churches, but also stressed that they should not retaliate.

Neighbourhood groups were being mobilised to look out for any potential trouble, he said, while adding that they would not be armed and would notify the police of any suspicious behaviour.

“We have been alerting the government that they must do something,” said Saidu Dogo, secretary for 19 northern states for the Christian Association of Nigeria.

“No country has ever survived a religious war, so the government must address the problem.”The sultan said after his meeting with Jonathan that the president agreed to look at previous reports issued by government panels on the violence linked to radical Islamists and the country's sectarian divisions.

The Muslim leader also said that more discussions would be held with religious and traditional leaders and Jonathan.

Previous studies on Boko Haram have delved into the roots of the crisis in Africa's most populous nation and largest oil producer, including poverty in the north and alleged political links to some who have been involved in violence.

The reports have produced no visible changes despite the government's pledges to take them into consideration.

There have also been major concerns, particularly among Western nations, over whether Boko Haram has links with outside extremists.

General Carter Ham, the head of the US military's Africa Command, has said that Al-Qaeda's north African branch, Shebab militants in Somalia and Boko Haram have expressed a will to work together, adding they also posed a threat to the United States.

On Tuesday, a spokeswoman for Ham confirmed his “continuing concern regarding the growing operational abilities of the group known as Boko Haram and of its stated intent to collaborate more closely with other terrorist organisations.”