YAOUNDE, Cameroon (AP) — The president of Nigeria made his first official state visit to neighboring Cameroon on Wednesday, as the two former enemies struggle to contain the mutual threat posed by Islamic militants carrying out suicide bombings across the region.

New Nigerian leader Muhammadu Buhari came to Cameroon's capital to bolster support for a multinational army to fight the Boko Haram uprising that has claimed at least 60 lives in recent days in Cameroon alone.

The violence has displaced nearly 2 million people and killed 20,000 across the region where the borders of Nigeria, Niger, Cameroon and Chad meet in the course of the 6-year uprising.

Attacks have mounted over the past year in Cameroon's far north and in Chad's capital as the militants seek retaliation for those countries' military aid in the Nigerian army's fight against Boko Haram.

The group drew international prominence when it abducted nearly 300 girls from Chibok, sparking an international campaign for their return that has stalled. Girls and young women have increasingly been used as suicide bombers in attacks on civilians.

Also complicating the fight has been the long-tense relations between Cameroon and Nigeria, and concerns over the role of Chad's military might on Nigerian soil. The U.N. Security Council has issued a statement calling for "increased regional cooperation."

Hard feelings between Nigeria and Cameroon date back to a 1980s land dispute. More recently, Nigeria accused Cameroon of doing little to prevent Boko Haram from using their territory as a refuge.

Cameroon saw Buhari's failure to visit earlier as a snub after he traveled to Niger and Chad, and the Cameroonian president, Paul Biya, didn't attend Buhari's May inauguration.