Extremists from three neighboring countries are fighting in Nigeria’s northeastern Islamic uprising, according to an alleged captured extremist whose account reinforces fears that one of Africa’s most powerful Islamic militant groups is growing closer to al-Qaeda affiliates and that radical movements are spilling across national boundaries.

“We do have members from Chad, Niger and Cameroon who actively participate in most of our attacks,” said a young man presented to journalists Friday night by Nigeria’s military as a captured fighter of the Boko Haram terrorist network.

The claim of foreign fighters indicates the growing influence of Boko Haram, which began as a machete-wielding gang and now wages war with armored cars, rocket-propelled grenades and improvised explosive devices in its mission to force all of Nigeria — a country of 160 million that has almost equal numbers of Christians and Muslims — to become an Islamic state.

Boko Haram poses the biggest security threat in years to the cohesion of Nigeria, already riven by sectarian, tribal and regional divisions that often explode into bloodletting, amid power struggles ahead of elections in 2015 that are expected to be contested by President Goodluck Jonathan, a fundamentalist Christian.

A harsh military crackdown in three northeastern states covering one-sixth of the country since mid-May has forced Boko Haram out of major cities and towns, but the security forces appear unable to prevent regular extremist attacks on soft targets such as schoolchildren that have killed hundreds in recent months.

Jonathan’s government, which is struggling to control the Islamic rebellion, for the first time presented an alleged Boko Haram fighter, a 22-year-old using crutches because of a bullet wound suffered when he was captured in a recent attack.

The man refused to give his name, for fear that his family would be targeted. His account sheds new light on life inside the shadowy Boko Haram, which means “Western education is forbidden” in the Hausa language.

The captured extremist said religion did not figure in his life as a Nigerian Islamic warrior, insisting his leaders “had never once preached Islam to us.” He said Allah’s name is invoked only when “we are running out of food supply in the bush. Our leaders will assemble us and declare that we would be embarking on a mission for God and Islam.”

He added: “I did not see any act of religion in there. We are just killing people, stealing and suffering in the bush.”

Recently, Boko Haram has carried out brutal attacks mainly on Muslim civilians. The new assaults “offer vital and disturbing insights” that “not only confirm many of the group’s earlier developments but also al-Qaida in the Islamic Maghreb’s, or AQIM’s, growing influence over it,” Jonathan Hill, senior lecturer at the Defense Studies Department of King’s College in London, wrote in an analysis published online this month at AfricanArguments.org.

“These atrocities bear many striking similarities to those carried out by AQIM and its various forbears in Algeria,” wrote Hill, who is the author of “Nigeria Since Independence: Forever Fragile?

Justice Minister Mohammed Adoke said last week that Boko Haram is being influenced from abroad, although he did not elaborate.

Boko Haram fighters, including leader Abubakar Shekau, were reported fighting alongside al-Qaeda-affiliated groups that seized northern Mali last year. The movement has boasted that it has fighters trained in Somalia by al-Shabab, the group that claimed responsibility for the deadly attack on Kenya’s upscale Westgate Mall last month.

— Associated Press