"The group had perfected plans to attack the United Kingdom and American Embassies and other western interests in Abuja", a DSS spokesperson told Reuters.
The vice president hinted that one of the challenges of freeing the girls was the existence of two factions in Boko-Haram, with each faction holding on to some of the girls.
Authorities arrested five more suspected Islamist militants in Benue state, in the country's middle belt, and Abuja between March 25 and 26, the security agency said.
Most were girls.The Boko Haram insurgency is now in its eighth year with little sign of ending, having claimed over 20,000 lives.
Nearly 1,500 children were detained past year, a Unicef spokeswoman said, as people fear their intentions when they are near checkpoints or markets in Chad, Cameron, Nigeria and Niger.
Government forces are intensifying aerial and ground patrols in the country's northeast.
The revelation comes as US officials confirmed that the Trump administration is expected to move ahead with the sale of high-tech aircraft to Nigeria for its campaign against Boko Haram.
FIVE insurgents suspected to be members of the Boko Haram terrorist group have been arrested by operatives of the Department of State Services (DSS).
Another 20-year-old Boko Haram member was arrested March 22 in Yobe state and "confessed his involvement in executing the sinister activities of the group".
In interviews, many children who have been associated with Boko Haram report that they keep their experience secret because they fear the stigmatization and even violent reprisals from their community. It has increasingly used children, especially girls, as suicide bombers.
In a statement released by the regional director for West and Central Africa for UNICEF, Marie-Pierre Poirier, said the children being used are victims and not perpetrators.
"The number of children used in "suicide" attacks in the Lake Chad conflict has surged to 27 in the first quarter of 2017, compared to nine over the same period past year", the report "Silent Shame: Bringing out the voices of children caught in the Lake Chad", crisis stated.
Attacks have also taken place in neighbouring Cameroon and Niger.
"We must also remember that the Chibok girls are not the only ones who have been suffering such violence at the hands of Boko Haram", the United Nations special rapporteurs said. At that time, officials said they were pressing on with negotiations and expected the release of a second group but no more have been freed.
Boko Haram had seized 276 pupils from the Government Girls Secondary School in Chibok on the night of April 14, 2014.