ABUJA, Nigeria (AP) — An armed gang has killed more than 100 people in a remote part of northern Nigeria, survivors and local authorities said on Tuesday.

The attackers targeted four villages in the Kanam area of Plateau State, the most recent in a series of violent attacks in Nigeria’s north.

Such attacks in Nigeria’s northern region have become frequent, especially between Fulani Muslims who are mostly cattle herders and Christian communities from the Hausa and other ethnic groups who are mainly farmers.

The conflict over access to land and water has further worsened the sectarian division between Christians and Muslims in Nigeria, Africa’s most populous nation with its 206 million people deeply divided along religious lines.

In this recent attack, the assailants arrived Sunday afternoon, ransacking houses and shooting at residents, according to Alpha Sambo, a survivor and Kanam youth leader who is helping those displaced and injured.

“The people that have been killed are more than 100,” he told The Associated Press on Tuesday. Other witnesses say as many as 130 died and many have been injured and displaced.

The police and the state government confirmed the attacks but did not give details on the cause or number of casualties. Authorities in Nigeria have in the past been accused of withholding information about death tolls in such killings.

On social media, videos viewed by AP appeared to show razed houses and bodies wrapped in mats and bags in mass graves. Many were buried even before their loved ones heard of their demise, residents said.

While there was no immediate claim of responsibility for the latest violence, residents said it was carried out by the herdsmen.

The assailants “were well-armed” with AK-47 rifles and machetes and arrived on dozens of motorcycles each carrying up to three men, said youth leader Sambo.

Two days after the attack, the Kanam area is still tense and calm has not been fully restored, Dayyabu Yusuf Garga, chairman of the Kanam local government authority, said.

Plateau State Governor Simon Bako Lalong directed security forces to restore peace and order in the affected villages and vowed “to make it difficult for terrorists and other criminals to set their bases in any part of the state,” according to a government statement.

The State Security Council has adopted “far-reaching measures to strengthen all security measures,” Lalong said, but similar commitments made in the past have not succeeded in improving security in the area, say residents.

President Muhammadu Buhari was elected in 2015 on promises that he would improve Nigeria’s security and is facing growing pressure to curb the killings as he reaches the end of his second and final four-year term as the country’s leader.

The West African nation continues to grapple with security challenges in other parts of the country. A decade-long insurgency in Nigeria’s northeast by the Islamic extremist rebels of Boko Haram and violence by armed groups in the northwest have led to the deaths of thousands more.

Nigerian security forces are often outnumbered and outgunned by the armed groups in those volatile areas, say security analysts, creating a serious challenge to Nigeria’s quest for peace and stability.