ABUJA: Nigeria's leader has ordered the arrest of the former president's national security adviser for allegedly stealing billions of dollars meant to buy weapons to fight Boko Haram Islamic extremists rampaging across northeast Nigeria.

"Thousands of needless Nigerian deaths would have been avoided" if the money had been properly spent, Femi Adesina, an adviser to President Muhammadu Buhari, said in a statement Tuesday night.

The order follows an interim report by a presidential committee that uncovered fraudulent and fictitious arms contracts amounting to $5.4 billion, Adesina said. The committee is investigating arms procurement since 2007 as part of the fight against endemic corruption that Buhari has waged since taking office in May.

Buhari has also ordered the arrest of other former high-ranking officials linked to the scandal, said Adesina.

Sambo Dasuki, a key adviser to former President Goodluck Jonathan from 2011, is accused of awarding "phantom contracts" to buy 12 helicopters, four fighter jets and munitions worth $2.9 billion that never were supplied. Buhari fired him in July.

Dasuki denied any wrongdoing in an interview Tuesday night with the PR Nigeria news agency, and said he was proud that in the final months under his watch Nigeria's military ousted Boko Haram from its self-declared Islamic caliphate in the country's northeast.

That offensive came as Jonathan faced elections. In the year before, soldiers fled before the extremists, allowing them to take control of a large swath of northeast Nigeria. Soldiers told The Associated Press they were going into battle without food and armed with just 30 bullets each.

Critics had questioned the ineffectiveness of Nigeria's once-powerful military forces despite an annual defense budget of between $5 billion and $6 billion, supplemented last year by a loan of $1 billion.

Nigeria's social media buzzed with the news Wednesday. "The war against Boko Haram under Jonathan was only a money-making machine for Sambo Dasuki, service chiefs and defense contractors," charged A. S. Aruwa.

"Beyond corruption, Dasuki should be charged for high treason: Men, women and children died because their armed forces could not defend them," added D. Olusegun.

There were also comments about revenge and pay-back. Dasuki is said to have arrested Buhari, a former military dictator who seized power from a democratically elected government, when he was ousted in a palace coup in 1985.

Nigeria's intelligence agency, the State Security Service, has kept Dasuki under house arrest for more than a week despite a Federal High Court order allowing him to travel abroad for medical care. The court had allowed Dasuki bail after he pleaded innocent to other charges of money-laundering, involving more than $423,000 found in cash, and illegal possession of arms seized at two of his homes.

Tuesday's move could pre-empt the court's demand for the attorney general to appear before it next week to explain why its order is being flouted. Dasuki also is fighting a prosecution request for his trial to be held in secret, to protect witnesses.

State Security, formerly controlled by Dasuki, said he refused to answer the committee's questions about the arms deals but Dasuki said he was never asked.

Dasuki, 60, had usurped the role of the Ministry of Defense in procuring weapons. He was called before a Senate committee last year to explain South Africa's seizure of $9.3 million in cash and a $5.7 million bank transfer that South Africa blocked, saying it involved an illegal arms deal. Dasuki said the deals were legitimate.

A retired army lieutenant-colonel, Dasuki participated in every coup in Nigeria since the 1980s.