Lagos , Nigeria ( CNN ) -- Three North Korean doctors serving at a hospital in Nigeria 's northern Yobe state were killed early Sunday morning , police said . There were mixed reports initially on where the victims were from , but the police chief of Yobe told CNN they were North Korean physicians assisting at Potiskum General Hospital as part of a government agreement . The government in Pyongyang has not confirmed that the victims were North Korean nationals . Authorities say 10 suspects are under arrest . `` At this point we can not say if they are Boko Haram , hired killers or common criminals , but we have cordoned off the area and are in the process of interrogating them , '' Commissioner Sanusi Rufa ' i said . Boko Haram is an Islamist militant group that has carried out scores of attacks across the north over the years . The group , whose name means `` Western education is forbidden , '' has referred to itself as the Nigerian Taliban . It seeks to overthrow the government and replace it with a regime based on Islamic law . Sunday 's predawn slayings came on the heels of another deadly attack against medical workers . On Friday , nine health workers who were administering polio vaccinations were killed in Kano , the biggest city in northern Nigeria . The victims , eight women and one man , were working for a government program established to vaccinate people across Nigeria .
The doctors were assisting a local hospital , police chief says . Ten suspects have been arrested , but police do n't know who 's behind the slayings . On Friday , nine health workers giving polio vaccinations were killed in Nigeria 's largest city .