( CNN ) Boko Haram fighters have carried out their first known lethal attack in Chad , the U.N. refugee agency said Friday , as the threat from the Nigeria-based Islamist militants spills over into neighboring nations . The fighters killed four civilians and a soldier in the predawn attack on the fishing village of Ngouboua on the shores of Lake Chad , according to residents and Chadian security sources . The attack came hours after 21 people were killed in two separate attacks on Akida ‎and Mbuta villages near the northeast Nigerian city of Maiduguri , according to residents and a local community leader . Adrian Edwards , spokesman for the U.N. High Commissioner for Refugees , told reporters in Geneva , Switzerland , that news had come in overnight of the attack on Ngouboua and details remained hazy . `` We are still getting information about how many people affected , we know that thousands of refugees were there , '' he said . `` The reports that we 've received , the town was attacked by about 30 militants using boats , they attacked parts of the town itself , the 'chef de canton ' himself was killed . We were in contact with a refugee during the attack but the phone line went dead . We are still trying to find out more about the situation there . '' Mamadou Dian Balde , of the UNHCR in Chad , later told CNN that the chef de canton , or local leader , who was killed had been `` a great champion of refugee protection . '' Authorities have not yet confirmed the final death toll , he said . But reports from the ground indicate three-quarters of the village was torched by the attackers and many residents have fled to surrounding areas . The village was peaceful and had generously taken in many refugees from the conflict in neighboring Nigeria , he added . The violence in northeast Nigeria has caused more than 157,000 people to flee into Niger , Cameroon and Chad , Edwards said . Some 100,000 of those are in Niger , 40,000 in Cameroon and the remainder in Chad . Nearly 1 million more people are believed to be internally displaced inside northeast Nigeria , according to that country 's national emergency management agency , Edwards said . `` With the violence that 's plagued northeast Nigeria spilling over into Niger , Cameroon and Chad , UNHCR is now calling for urgent humanitarian access to refugees and internally displaced people in these countries to provide urgently needed assistance , '' he said . `` For many refugees , for locals , for aid workers too , the situation is now becoming increasingly terrifying . '' Earlier this month , several African nations -- including Nigeria , Niger , Benin , Cameroon , and Chad -- pledged to deploy 8,700 troops , police and civilians as part of a regional effort to fight Boko Haram . The assault by Boko Haram on Chadian soil may be a response to that initiative . An attack earlier this month by Boko Haram militants against Chadian soldiers on the border between Cameroon and Nigeria left 13 dead and 21 injured , the United Nations said last week . The Chadian soldiers were deployed to fight Boko Haram in Cameroon and Nigeria . CNN 's Lucy Pawle and Radina Gigova contributed to this report .
Boko Haram has carried out its first known deadly attack in Chad , U.N. agency says . The group is suspected of carrying out a series of attacks on schools and churches since last year.