Yobe state police commissioner Sanusi Rufai said it was nevertheless too early to know who was behind the attack, which happened either late on Saturday or before dawn on Sunday.
Abuja officially became the Nigerian capital in 1991, and has recently been in the spotlight following drastic measures by the city's high-profile minister Nasir el-Rufai to ensure the area's "master plan" is followed.
Rufai said officers had made 10 arrests after the killings, though police in Nigeria routinely round up those living around the site of a crime, whether or not there is any evidence suggesting their complicity.