Nigeria’s President Muhammadu Buhari has ordered the arrest of an advisor to former leader of the west African nation for stealing more than $2 billion meant to fight a deadly Islamic militant group Boko Haram.

Sambo Dasuki, 60, the security advisor to former Nigerian President Goodluck Jonathan from 2011 to 2015, is accused of siphoning the money through “phantom contracts” to buy 12 helicopters, four fighter jets and munitions worth a total $2.9 billion meant to fight Boko Haram.

A report by a presidential committee to uncover fraudulent and fictitious arms contracts amounting to $5.4 billion between 2007 and 2015, showed that the former presidential advisor was linked to the disappearance of the money.

According to a statement from the president’s office, the investigation “unearthed several illicit and fraudulent financial transactions”.

A career soldier, Dasuki, was also at the centre of a row over Nigeria’s unorthodox arms procurement in 2014, when South Africa seized suitcases packed with millions of dollars of cash at an airport in Johannesburg.

Nigeria’s defense forces is funded anything between $5 billion and $6 billion annually in the country’s budget.

Despite the huge budget, the army has on several occasions complained that they are ill-equipped to fight the Islamic militants, who have terrorized the north-eastern part of the country and neighboring Cameroon.

Boko Haram, considered the second most dangerous extremist group in the world after ISIL, have killed thousands of people in West Africa and kidnapped others in their fight to introduce sharia laws in the region.

While some in Nigeria called for Dasuki to be charged with high treason, others felt President Buhari was using his office to settle his long standing battle with the ex-official.

Dasuki arrested Buhari, a former military dictator who seized power from a democratically elected government, when he was ousted in a palace coup in 1985.