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 cannot 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.