Christian leaders in North East Nigeria have warned that Boko Haram insurgents are attempting to wipe out Christianity from areas they control.

In a statement after a day conference, four senior clerics – the Roman Catholic bishop of Yola, Rt Rev Stephen Dami Mamza, the archbishop of the Lutheran Church of Christ in Nigeria (LCCN), Most Rev Nemuel Babba, the president of the Ekklesiyar Yan'uwa a Nigeria, Samuel Dali Danti, and LCCN bishop, Amos Yakubu – called on politicians there including the country's president, Goodluck Jonathan, to suspend all political activities and focus on defeating the Boko Haram insurgents.

The call came after a suicide bomber killed at least 48 young people at a school in Yobe State, injuring many more. The Islamist movement has been responsible for thousands of deaths, mainly Muslim, and tens of thousands of internal displacements. It has recently begun taking and holding territory.

The communiqué said: "The Christian leaders are worried over the recent takeover of six local governments in Adamawa State namely; Madagali, Michika, Mubi North, Mubi South, and parts of Hong and Maiha Local Governments by the insurgents.

"We are also worried that the Christians are been systematically eliminated by members of the Boko Haram Islamic extremists. We are forced to believe that the whole attack is a deliberate plan to exterminate Christians living in the affected areas."

The Church leaders said that churches in captured territories were completely destroyed by the insurgents, and warned of the danger of downplaying the significance of their actions. They said: "We reject in strong terms insinuations from certain quarters that the insurgents are a mere bunch of trigger-happy miscreants whose intentions are to settle certain scores with the government owing to the towering revelations of attacks mostly targeted against Christians.

"We are therefore tempted by these circumstances to believe that the whole onslaught is a deliberate attempt to exterminate Christians in the captured region."

Nigeria's military has been criticised for its failure to deal with the insurgents and its tactics, which are alleged to include torture and summary executions, in its campaign against them. The US government has refused to sell Nigeria heavy weapons for use against Boko Haram because US law bans the sale of lethal weapons to countries whose military are accused of gross human rights abuses.