ABUJA, Nigeria (AP) — Gunmen ambushed and killed security personnel who were on patrol in communities in Nigeria ‘s Plateau state, according to the state government.

The government did not specify the number of casualties, but the Kanam Development Association (KADA), a local group, claimed 20 personnel, including two senior military officers and eight local security operatives, were killed in the ambush.

The ambush happened on Friday around Wanka, Kyaram and Gyambau communities located in the Kanam area of Plateau state. No group has claimed responsibility for the attacks.

The state government on Sunday condemned the attack and said the security agencies are implementing measures to intensify surveillance and reinforce security presence across vulnerable communities.

“For over three to four years, these communities have been subjected to repeated attacks, cattle rustling, kidnappings, and destruction of property by armed bandits who appear to operate with alarming freedom,” KADA said in a statement on Saturday.

For years, Nigeria has been battling a complex security crisis from different armed groups, especially in the northern part of the country.

Among the most prominent Islamic militant groups are Boko Haram and its breakaway faction, which is affiliated with the Islamic State group and known as Islamic State West Africa Province. There is also the IS-linked Lakurawa, as well as other armed groups that specialize in kidnapping for ransom and illegal mining.

The crisis has worsened recently to include other militants from the neighboring Sahel region, including the Jama’at Nusrat al-Islam wal-Muslimin, which claimed its first attack on Nigerian soil last year.

Several thousand people in Nigeria have been killed, according to data from the United Nations. Analysts say not enough is being done by the government to protect its citizens.

The United States has sent troops to the West African nation to help advise its military on the fight against insecurity.