Secret police in Nigeria say they arrested two members of the Boko Haram group before the bombing of the United Nations headquarters in the capital, Abuja, last Friday.
Boko Haram says it carried out the suicide attack which killed 23 people
and wounded more than 80.
A secret police statement said two suspected members of Boko Haram were on 21 August, following a warning of attacks in the capital.
A third member of the group who returned from Somalia recently, is suspected of being the leader of the plot.
The BBC reports that, loosely translated from the Hausa language, Boko Haram means ''Western education is forbidden''.