Abuja - The former national security advisor and an ex-junior finance minister have been hauled in for questioning over a disputed $2 billion arms deal, sources told AFP on Tuesday.
Sambo Dasuki was brought to the secret police headquarters in Abuja on Tuesday after he was accused of awarding "fictitious and phantom contracts" for weapons to fight Boko Haram.
A senior official at the Economic and Financial Crimes Commission (EFCC) later said Bashir Yuguda, a former minister of state for finance under president Goodluck Jonathan, was arrested on Monday.
An official from the NSA's office was also detained, he added, requesting anonymity.
Also Read: SSS arrests ex-NSA, Sambo Dasuki again
"Today (Tuesday) they brought in the former governor of Sokoto state (in northwest Nigeria), Attahiru Bafarawa, and (media magnate) Raymond Dokpesi," the source said.
"The arrests made are in connection with the arms contract scandal."
President Muhammadu Buhari said last month that Nigerian troops were denied weapons to fight Boko Haram and thousands of lives were lost because of rampant fraud in the procurement process.
He ordered anyone involved in corrupt multi-billion dollar deals for weapons and equipment to be "brought to book" after receiving a report from a committee set up to probe the issue.
Dasuki, a former army colonel, is accused of awarding some $2 billion in bogus deals for fighter jets, helicopters, weapons and ammunition that never materialised.
He has denied the charges, claiming all contracts and payments were sanctioned by Jonathan as president and commander-in-chief, and that he was never asked to give evidence to the committee.
Also Read: EFCC arrests Dokpesi
The 60-year-old is already facing money laundering and illegal possession of weapons charges. He claims he is the target of Buhari's anti-corruption campaign.
The president has launched a crackdown on endemic graft since taking office in May but the allegations about non-existent arms contracts risk laying bare claims of a rot in the military.
Under Jonathan, Boko Haram captured swathes of territory in its quest for a hardline Islamic state in the remote northeast, threatening Nigeria's sovereignty.
Troops regularly complained they lacked the weapons and equipment to fight the better-armed rebels until the involvement of armies from neighbouring countries joined the fight in January.
The insurgency has left at least 17 000 dead since 2009 and made more than 2.6 million people homeless.
Last month, Boko Haram was named in the latest Global Terrorism Index as "the most deadly terrorist group in the world", having killed 6,633 people last year.
The index, published by the Institute for Economics and Peace think-tank, said the Islamic State group, to which Boko Haram has pledged allegiance, killed 6 073.