At least 25 people were killed in separate attacks in northern Nigeria, police said on Thursday, putting the spotlight on rising levels of rural violence in the country.Thirteen people were killed in prolonged clashes between cattle thieves and local civilian militia in the northern state of Zamfara.In Adamawa, in the northeast, at least 12 people were killed in an attack on several villages.The attacks underlined the diversity of Nigeria's security threats that persist in the absence of a robust police force and efficient judicial system.In Zamfara, the militia and cattle thieves fought a gun battle on Tuesday through Wednesday in the remote village of Fankashi in the Maru district, police spokesperson Mohammed Shehu told AFP."Our men recovered 13 dead bodies from the criminal gang and the vigilantes from the village after the fight," he added.The village was attacked by the bandits, resulting in the fight with the militia, who were armed with locally made, single-shot muskets.Police reinforcements were later sent to the area, said Shehu.In Adamawa, state police spokesperson Othman Abubakar said there was an overnight attack on Wednesday in the Numan district that saw scores of homes torched. "From reports sent to us by the divisional police officer from Numan, 12 people were killed in the attacks and 150 homes were destroyed by unknown gunmen," said Abubakar. Local chairperson Arnold Jibila said the death toll was higher and that 30 people were killed by suspected "herdsmen." "Search teams are still combing the bushes and the river for more bodies. We don't know what they will come up with," Jibila said.Nigeria is in the grip of a security crisis as nomadic herders and sedentary farmers fight over land in an increasingly bloody battle for resources. Rural communities in Zamfara have been under siege for several years from cattle rustlers and kidnapping gangs, who have raided herding communities, killing, looting and burning homes.To defend themselves, villages and herdsmen form vigilante groups, but they too are often accused of extra-judicial killings and provoking a bloody cycle of retaliatory attacks. Nigerian President Muhammadu Buhari has been criticised for failing to curb the violence, which is becoming a key election issue ahead of the upcoming presidential polls in 2018. Military and police are overstretched in Nigeria, which, along with fighting Boko Haram jihadists in the north, is battling militants and pirates in the oil-rich south, a simmering separatist movement in the east and a bloody battle between herdsmen and farmers spanning the vast central region.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.