Nigeria’s military said it arrested the alleged leader of Islamist militant group Ansaru, an offshoot faction of Boko Haram, which became known for kidnapping foreign nationals.

Khalid al-Barnawi, who was among three Nigerian insurgent leaders listed as terrorists by the U.S. government, was detained in the central city of Lokoja on April 1, Brigadier-General Rabe Abubakar, a military spokesman, said by phone on Sunday.

Al-Barnawi, also known as Mohammed Usman, has ties to Boko Haram and al-Qaeda in the Islamic Maghreb, the U.S. State Department said in 2012. Two years later, the department offered a $5 million reward for information leading to the location of al-Barnawi.

Ansaru claimed responsibility for holding French engineer Francis Collomp for almost a year before he was freed in November 2013. The group also killed seven foreigners working for Setraco Nigeria Ltd. when they were seized in a February 2013 attack at their residential compound in the northern state of Bauchi. Ansaru said it carried out the attack in response to “the transgressions and atrocities done to the religion of Allah” by European nations in countries such as Mali and Afghanistan.

Insurgents Arrested

The group also raided a police station in the Nigerian capital, Abuja, in November 2012, killing officers and freeing detained militants.

Boko Haram, the more widely known group, is in the seventh year of a violent campaign to impose its version of Islamic law. President Muhammadu Buhari has repeatedly said his government has beaten back the militants since he came to power in May and that they no longer hold territory in the northeast, but the fighters are still carrying out suicide attacks and massacres.

In a separate statement late Sunday, army spokesman Colonel Sani Usman said troops captured six Boko Haram insurgents in the northeastern villages of Kadawu and Garna and recovered explosive devices.