Suspected Boko Haram terrorists killed 17 herders and stole their cattle following clashes in the troubled northeastern Nigerian state of Borno, self-defense militia told AFP Monday.

The militants on Saturday attacked herders guarding their cattle in a pasture near Airamne village in Mafa district, the militiamen said.

"Seventeen herders were killed in the fight and all their cattle taken away," militia leader Babakura Kolo said.

"The herders put (up) resistance but were outgunned and outnumbered by the attackers, who had better weapons," said Kolo.

Another militiaman, Ibrahim Liman, gave the same toll.

He said the terrorists launched the attack from camps in nearby Gajiganna forest, where they relocated after being partially forced out from their stronghold in Sambisa forest by terrorist rivals ISWAP and the Nigerian army.

ISWAP – Islamic State West Africa Province – split from Boko Haram in 2016 and rose to become the dominant group in the region's long-running terrorism turmoil.

It seized swathes of territory under Boko Haram control after leader Abubakar Shekau was killed in clashes with ISWAP in May last year.

Boko Haram and ISWAP have increasingly been targeting civilians, particularly loggers, farmers and herders, accusing them of spying on them for the military and the local militia.

But herders who pay a levy to the terrorists are usually allowed to let their cattle graze safely in territory under militant control.

Terrorist violence in the northeast has killed over 40,000 people and displaced around 2 million from their homes since 2009, according to the United Nations.

The conflict has spilled into neighboring Niger, Chad and Cameroon, prompting the creation of a regional military force to fight the terrorists.

The killings, abductions and looting in the northeast are part of an overall security crisis in Nigeria.

Voters go to the polls on Feb. 25 to elect a successor to President Muhammadu Buhari, who is stepping down after two terms, the constitutional limit.