A man holds a sign that reads 'Bring back our girls' during a protest outside Nigeria House in London on May 9, 2014. dan kitwood/getty images

Nigerian troops freed over 5,000 Boko Haram captives in the northeastern Borno state, the country’s army said Sunday. Eight members of the Islamist militant group were also in killed in the operation, which the army has codenamed Lafiya Dole.

The operation — whose name translates roughly to "peace by all means" — took place in four villages of Borno state. Weapons, ammunition and transport equipment like motorcycles were recovered from the raided camps around Mafa, a local government headquarter in the state, Col. Sani Usman, spokesman of the Nigerian army, said, according to local news portal Premium Times.

Boko Haram
A banner shows pictures of 100 most wanted Boko Haram suspects, released by the Nigerian Army Chief Lt. Gen. Tukur Buratai in northeast Nigerian town of Damboa, Feb. 27, 2016. Getty Images/STRINGER/AFP

Boko Haram, which translates to “Western influence is a sin,” has killed thousands of people and displaced around 1.5 million in order to establish an Islamic caliphate in northeastern Nigeria. Over the last seven years, the group has used female suicide bombers and homemade explosives. However, the group has reportedly suffered setbacks recently, following counterattacks by the government.

Last month, the United Nations Security Council said Boko Haram’s links with the Islamic State group, also known as ISIS, were a matter of concern. Boko Haram pledged allegiance to ISIS in 2015 and continues to “undermine the peace and stability” in West and Central Africa, the Security Council said.

The council members demand that Boko Haram “immediately and unequivocally cease all violence and all abuses of human rights and violations of international humanitarian law.”

The extremist group, which has been active in Nigeria since 2009, stepped up its activities across Nigeria’s borders in Cameroon, Chad and Niger in 2015.