Tighter restrictions imposed by the authorities on aid groups operating in northeast Nigeria's conflict zone are "stifling" efforts to tackle the humanitarian crisis, Human Rights Watch said on Wednesday. Military and civilian authorities last year stiffened official controls over organisations operating in the region, in a clampdown the rights group said made transporting staff and aid more difficult. "Undue restrictions are intensifying the suffering of vulnerable people in dire need of life-saving assistance," Anietie Ewang, Nigeria researcher at Human Rights Watch, said in a statement.The measures come as humanitarian organisations face growing dangers from Islamist groups in northeast Nigeria, with 12 aid workers killed in 2019.The United Nations has said there are an estimated 1.2 million people in the region "who cannot be reached by the humanitarian community", a 30% increase on 2018. The stiffer demands by the authorities followed a surge in attacks by jihadists who have waged a decade-long uprising that has killed more than 36 000 people.Human Rights Watch said the tighter requirements include "lengthy processes" to get authorisation for transporting personnel, cash and aid as well as mandating military escorts in some areas and limiting fuel supplies."Aid workers said that the amount of control the Nigerian military now has over their activities prevents them from reaching millions of people and causes safety concerns as other parties to the conflict may view aid groups as taking the government's side," the rights groups said. Nigeria's military has long viewed aid organisations operating in the northeast with suspicion.Last year the army closed the regional offices of international groups Action Against Hunger and Mercy Corps for two months over allegations they were collaborating with insurgents. Overall some 1.8 million people are displaced in northeast Nigeria and seven million are in need of urgent assistance. The jihadists have splintered into several groups, with one loyal to Boko Haram leader Abubakar Shekau and another affiliated to the Islamic State group.