The United Nations says violence has forced more than 2.4 million people to flee their homes in Nigeria, Niger, Cameroon and Chad.
It says more than nine million people across the Lake Chad region are in need of humanitarian assistance.
The World Health Organisation has declared the humanitarian crisis in Nigeria's northeast to be on par with the crises in Syria and Yemen.
Regional officials say the humanitarian crisis has been triggered by militant groups, including Boko Haram.
Chad's President, Idriss Déby, says this threat could spread further across the continent.
"Africa today is bearing the full brunt of terrorism - the threat of the century. Somalia, Libya, Mali, the Lake Chad region. The Sahel as a whole is seriously destabilised and the danger is threatening to spread across the continent."
Nigerian President Muhammadu Buhari says his country is greatly affected.
"Of particular concern to us in Nigeria is the plight of Internally Displaced Persons arising from Boko Haram terrorism. We have taken concrete steps to address their humanitarian needs and to ensure that necessary conditions are established to enable the voluntary return of the displaced persons to their places of abode in safety and dignity."
Steve Purbrick is Oxfam Australia's Emergency Security Coordinator in Nigeria.
He says most of the people affected are in northeast Nigeria.
"We've seen an escalation of the humanitarian impact. So loss of livelihoods, massive, massive displacement. But also a level of violence that has stopped people moving about and that's what's concerning us most because people are not able to reach safety and also not able to reach any kind of food and difficulty accessing any water, difficulty accessing any kind of income as well. We're facing a critical humanitarian crisis without much funding because the Lake Chad Basin is the farthest corner of the world."
The UN says about three million people are facing severe food insecurity in the region.
It says in the far north of Cameroon, the number urgently needing food aid has quadrupled in the last year.
Steve Purbrick says if the international community and affected countries don't address the crisis, there will be large-scale famine.
"Famine is not a word we would ever use lightly in this context, it signifies the worst-case scenario. It's a genuine concern in this context because we have levels of child malnutrition that are above our threshold in declaring a famine. We have levels of mortality, so a number of people dying per day for a given population - again a bove that threshold. The thing we're missing is we don't have enough information because we simply can't get access to some of the areas where we know there are about two million people that are not accounted for and these are the areas that are most concerning to us."
He's appealing to the Australian government to also offer assistance.
"They haven't so far and the aid budget has been cut significantly in recent years. The first issue really is to get funds to ease the response here in west Africa."
