Nigeria's army said on Thursday they have arrested 17 people in connection with the killing of more than 200 people in the central state of Plateau. The recent clashes between cattle farmers and herders have put pressure on President Muhammadu Buhari to stop the violence, as he works to secure a second term in the 2019 presidential polls. Rising insecurity, from unrest involving farmers and herders, cattle rustlers, communal clashes, banditry and Boko Haram, is shaping up to be a key election issue. Amnesty International said at least 1 813 people have been killed in 17 states since the start of the year - more than double the figure for last year.Army spokesperson Major Adam Umar said three of the arrests were linked to killings in the Barikin Ladi area, while the other 14 were arrested in connection with the deaths of travellers in the south of the state capital, Jos. "We all know that some days back, some villages in Barikin Ladi were attacked and these three suspects were arrested in connection with that," Umar said."As our men were repelling the attacks in those areas, we arrested these three suspects with four rifles, three locally made guns and one AK47," he added.The clashes are rooted in tensions over access to land between the pastoral herders and sedentary farmers but have also generated sectarian friction between Muslims and Christians.Police and army reinforcements have been sent to Plateau to improve security, while a dusk-to-dawn curfew remains in place in areas of the state.A failure to arrest and prosecute perpetrators has long been pinpointed as a key factor in the cycle of violence, which has left thousands dead in recent decades.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook. Amnesty's Nigeria director Osai Ojigho said on Wednesday that security also needed to be improved, as not enough was being done to protect lives and property.She said there were "unacceptable security lapses" and called for an investigation into why there was no apparent response to the attacks for hours.The government needs to answer "who are these attackers, where do they come from, where do they go to after attacks, who arms them (and) why is the security forces' response time so slow?" she added.