The Department of State Security (DSS) said last Thursday's raids were based on "credible intelligence" linking Mohammed Sambo Dasuki -- who lost his job last week when President Muhammadu Buhari sacked the military top brass -- to "alleged plans to commit treasonable felony against the Nigerian State".
Agents found numerous weapons in simultaneous raids on three of Dasuki's properties in his northern home state of Sokoto and the capital Abuja, the DSS said in a statement late yesterday.
Under the Nigerian criminal code, treasonable felony can include planning to "remove during his term of office otherwise than by constitutional means the president as head of state of the federation and commander-in-chief of the armed forces".
The statement did not elaborate on the alleged offences.
Dasuki, 60, was unable to produce evidence of ownership of 12 new high-performance vehicles, five of which were bullet-proof, found on his premises, the DSS added.
Buhari's purge of top military commanders inherited from his predecessor Goodluck Jonathan was widely expected as the new president, who took office in May, aims at overhauling a military that struggled to take on the Boko Haram insurgency throughout 2014.
Dasuki, who was an army major in 1985, was reported to be among the team of soldiers who arrested Buhari after he was overthrown as Nigeria's military ruler in August that year.
He had served as national security adviser from June 2012 until his sacking last Monday.
