Nigeria's army says it has arrested the leader of the Islamist militant group Ansaru, a breakaway faction of Boko Haram.
Ministry of Defense spokesman Rabe Abubakar says Khalid al-Barnawi was arrested in the central city of Lokoja on Friday.
The U.S. government has offered a $5 million reward for al-Barnawi since 2012.
Ansaru emerged as a separate group from Boko Haram that year. Both groups aim to establish an Islamic state in Muslim-majority northern Nigeria.
The United States accused Ansaru of kidnapping and killing several foreign workers in Nigeria and killing Nigerian police officers during a 2012 attack on an Abuja police station.
It also said Ansaru has close ties to al-Qaida in the Islamic Maghreb, and designated Ansaru as a terrorist group in November 2013.