Security agents are besieging the home of Nigeria's former national security adviser, preventing him from leaving the country because he is refusing to answer questions about a $2 billion arms deal.

The Department of State Security said it wasn't illegally blocking the home of Col. Sambo Dasuki despite a court order releasing his seized passport for medical travel.

Family members said he did not fly Wednesday because of a tip-off he would be arrested. They said Dasuki told agents any new charges should be filed in court. State Security said he refuses to appear before a committee investigating the arms deal.

Dasuki has pleaded innocent to laundering $423,000 and illegally possessing a seized arms cache.

Corruption has dogged Nigeria's ability to combat an Islamic uprising that has killed 20,000 people.