Defence spokesman Brigadier General Rabe Abubakar announced on Saturday that Khalid al-Barnawi, leader of the militant group Ansaru, has been arrested by the Nigerian Army.
Ansaru is a splinter faction of Boko Haram that has been accused of kidnapping and killing Westerners.
In 2012 the US State Department put Khalid al-Barnawi’s name into three Nigerian militants blacklisted for ties to Boko Haram and Al Qaeda's North African wing.
General Rabe Abubakar announced that al Barnawi was arrested on Saturday in Lokoja, the capital of the central state of Kogi.
"We have made that giant stride," Abubakar said.
He also said some Boko Haram fighters had surrendered to Nigerian troops.
Nigeria's President Muhammadu Buhari has declared defeating militancy in Africa's most populated country, which also has the continent's largest economy, as a top priority.