Nigeria's military has arrested a number of security personnel over links to Islamist extremist group Boko Haram.
The arrests on Friday came after soldiers from a special military unit deployed in the northeastern city of Maiduguri arrested an immigration officer, Grema Mohammed, for allegedly being an active member of Boko Haram, a military spokesman said.
His confession led to the arrest of a number of other officials.
Boko Haram is blamed for deadly attacks that have killed more than 1,400 people since 2010 as part of its rebellion in northern and central Nigeria.
The arrest "led to further arrests of some other security personnel that had been participating in various terrorist attacks in Borno and Yobe states,"said Lieutenant Colonel Sagir Musa.
He did not specify how many arrests had been made.
"He confessed to being an active member of the Boko Haram terrorist sect which he joined long before the 2009 crisis," Musa said in a statement in reference to a 2009 attacks by the group.
"He also confessed to having been trained alongside 15 other members of the sect on weapon handling, assassination and special operations in Niger republic," Musa added, referring to the neighbouring nation.
Grema was arrested over a month ago at a checkpoint while allegedly impersonating as an army lieutenant.
The suspect also confessed to the killings of some senior civil servants, security personnel and politicians who had spoken against the sect in Yobe and Borno states.
Boko Haram shot to prominence in 2009 when hundreds of their members attempted to storm police stations and government buildings in Maiduguri.
The security forces quelled the rebellion and killed dozens of the group's members, as well as its leader, since then, their attacks have been better organised and caused many more civilian deaths.
Three of Boko Haram's leaders have been declared global terrorists by the US, but Washington has resisted calls to slap a terrorism designation on the entire organisation on the grounds that Boko Haram's primary focus is domestic.
US officials also say what has come to be known as Boko Haram may in fact be a number of different factions or groups.
Its main Islamist faction has said it wants to create an Islamic state in the north, but its demands have varied widely.