Starting in Mali, Islamist militants have gained ground in the Sahel, expanding further south to threaten West African coastal states while more groups are battling in the Horn of Africa, Lake Chad and Democratic Republic of Congo.

"The epicentre of terrorism has shifted from Middle East and North Africa into sub-Saharan Africa concentrated largely in the Sahel," UN Deputy Secretary General Amina Mohammed told the counter-terrorism summit in Abuja.

"The situation particularly in the Sahel is dire... the region now accounting for almost half of all deaths from terrorism globally."

Nigerian President Bola Ahmed Tinubu joined his counterparts Ghana's President Nana Akufo-Addo and Togolese President Faure Gnassingbe to urge more regional cooperation, intelligence sharing and work to create a standby military force.

"Such a force can stand as a strong deterrent to large-scale and protracted terrorist operations," Tinubu said.

Several African countries already cooperate in a multi-national joint military task force in the Lake Chad border areas.

Togo's Gnassingbe also called on the international community to do a better job in helping African nations finance their counter-terrorism operations.

Niger, Burkina Faso and Mali have been battered by years of conflict with Al-Qaeda- and Islamic State-allied jihadist groups but coups in all three have also hampered regional cooperation.

Last month, Niger said 23 of its troops had been killed in a "terrorist" ambush near the borders with Burkina Faso and Mali in an area where jihadist attacks are common.

But increasingly the violence has spread to the borders of coastal Gulf of Guinea countries, Ghana, Togo, Benin and Ivory Coast.

The withdrawal of French troops from the Sahel has heightened concern over the spread of violence.

One major concern is the millions of small arms in the hands of non-state groups in the continent, Nigeria's Foreign Minister Yusuf Tuggar said.

But he said African states also face new challenges in fighting jihadists such as the impact of the climate, the breakdown of cooperation with some nations, social media fake news and unregulated money transfers through crypto.

"Today the challenge of fighting terrorism is different in scale... We are fighting networks that know no boundaries or borders," he said.

"Africa finds itself on the front of everyone's war."