Abuja - Nigerian president Muhammadu Buhari on Friday said he was investigating more military top brass in an ever-widening probe into the alleged looting of funds intended for fighting Boko Haram.
The expanding corruption investigation was announced as the spokesman of Nigeria's main opposition Peoples Democratic Party was charged with having fraudulently received nearly $2 million.
Olisa Metuh was arrested last week as part of a probe by the Economic and Financial Crimes Commission (EFCC) into allegedly bogus arms deals.
The PDP spokesman and his private company are accused of receiving 400 million naira ($1.99 million, 1.83 million euros) from the Office of the National Security Advisor's central bank account.
Prosecutors allege they received the money from former national security advisor Sambo Dasuki "for political activities" of the PDP.
Dasuki is accused of diverting funds meant to buy weapons and military hardware by awarding "fictitious and phantom contracts" for jets, helicopters and bombs to the tune of $2 billion.
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At the time, the military was in dire need of weapons and equipment to fight back against Boko Haram, as they captured swathes of territory in Nigeria's northeast.
Dasuki was arrested in December last year and charged with fraud and money-laundering. He denies the charges and says all deals were sanctioned by former president Goodluck Jonathan.
A statement from Buhari's office on Friday said Nigeria's former most senior officer, ex-chief of defence staff Alex Badeh, was among 17 serving and retired officers facing a corruption probe.
Dasuki, a former army colonel, also figures on the list along with 21 companies.
The probe would look at "the roles of the officers and the... companies and their directors in fundamental breaches associated with the procurements" by Dasuki's office and the air force.
A panel looking into the procurement also highlighted deficiencies in equipment delivered, including helicopters without rotor blades and aircraft that were not airworthy, the statement said.
In some cases, equipment was over-priced or not delivered, it added.
A prominent PDP supporter, media magnate Raymond Dokpesi, and former defence minister Bello Haliru Mohammed have previously been arrested and charged with similar offences to Metuh.
Mohammed was former president Goodluck Jonathan's campaign manager in his failed bid for re-election in March this year.
Metuh entered a not guilty plea to seven charges when he appeared at a federal high court in the capital, Abuja. He was remanded in custody until next Tuesday pending a bail hearing.
The EFCC is spearheading a wide-ranging anti-corruption campaign by Buhari to root out endemic graft in Africa's most populous nation and leading economy.
The PDP has accused Buhari of leading a witch-hunt against it. A former political associate of the president, Lawal Jafaru Isa, was arrested last week as part of the arms procurement investigation.