JIBIA AREA, KATSINA STATE — Gunmen killed at least 15 people during attacks on two villages in northwestern Nigeria. The attacks targeted the neighboring communities of Falale and Kadobe in the Jibia area of Katsina State in the early afternoon, according to Nasir Mu'azu, Commissioner for Home Affairs in Katsina State.

Local security forces had previously killed three gunmen during a firefight in the area. The assault was carried out in retaliation for the earlier firefight, according to Mu'azu.

"Security forces have since restored order and stabilized the situation," Mu'azu said. "We appeal to residents to remain calm and allow security forces to complete their investigation."

No group has claimed responsibility for the attacks. Armed groups known as "bandits" regularly carry out raids and kidnappings for ransom in the northwest and north-central part of Nigeria.

The bandit groups include mostly former herders who took up arms against farming communities after clashes over increasingly strained resources, authorities have said.

An insurgency is being fought by the Boko Haram group and its splinter faction, the Islamic State West Africa Province in Nigeria. These groups are mostly active in northeastern Nigeria.

The security crisis in Nigeria has expanded to include militants from the neighboring Sahel region, including the Jama'at Nusrat al-Islam wal-Muslimin. The group claimed its first attack on Nigerian soil last year.

Several thousand people have been killed in Nigeria, according to data from the United Nations. The U.S. sent troops to Nigeria last month to help advise its military on addressing insecurity.