Speaking after the United States launched strikes targeting militants in Nigeria on December 25, General Dagvin Anderson, head of the US Africa Command (Africom), said the two countries had decided to "increase collaboration".

"We agreed that we needed to work together on the way forward in the region," Anderson told a virtual news conference.

"That has led to increased collaboration between our nations to include a small US team that brings some unique capabilities from the United States in order to augment what Nigeria has been doing for several years."

The general did not give details on the team's activities.

Trump has alleged there is a "genocide" of Christians in Nigeria, a claim rejected by the Nigerian government and many independent experts, who say the country's security crises claim the lives of both Christians and Muslims, often without distinction.

Nigeria, Africa's most populous country, is broadly split between a Christian-majority south and Muslim-majority north.

Africom told AFP last month the US military would increase equipment deliveries and intelligence sharing with Nigeria as part of efforts to fight Islamic State group jihadists.

The US strikes in December hit IS targets in Sokoto state, in northwestern Nigeria.

Africom said US military support would be concentrated in that region and the northeast, hit by nearly two decades of unrest blamed on Islamist group Boko Haram and a splinter movement, Islamic State West Africa Province (ISWAP).