Nigeria's state oil firm has denied failing to account for the money, saying the claim was "unsubstantiated".
Sanusi, who was out of the country, said he was unaware of what accusations the president's office was referring to and questioned the legality of his dismissal.
"I don't know what they are talking about. When I come back I will see what those allegations are," he told CNBC Africa.
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"There is also the legal question of (the) president, who does not have the legal authority to remove the central bank governor. Even if I challenged it – I will not go back to the job, but I think it would be in the interest of the institution for the court check if the president has the power," he said.
However, Abati said Sanusi had been under investigation since mid-2013, and that the central banker had been aware of this.
"He was aware of it and he was queried," Abati told CNBC Africa. "What you probably have in this situation, is a case of a man who knows that he has a case to answer and who has taken steps – preemptive steps – to prevent certain outcomes."
He added that "many Nigerians" approved of the suspension.
"I do not believe that anybody should have any anxiety about what happens hereafter. Indeed, what I have seen online is that many Nigerians – if not the majority of them – have been saying that the suspension of Mr Lamido Sanusi has been long overdue," he said.
Meanwhile, Sanusi said he hoped the news would not damage the Nigerian economy, as the bond market closed unexpectedly and the Nigerian naira spiked to 169 to the dollar.
"I also hope the position of the central bank will be protected. I have been fortunate to do some good work on the banks in terms of stability, I would not want to see all of that unravelled," he said.
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Sanusi's deputy, Sarah Alade, will replace him on an acting basis.
Sanusi said: "I think she is a very competent person, I have every confidence in her, I am very happy for her. Like I said I have no regrets, no ill feelings. I am happy and proud of what I have done," he said.
Abati refused to rule out the possibility that the Nigerian government might seek to prosecute Sanusi for his alleged offenses.
"I believe our government will do so if there are any grounds, but it is not for me to determine that," he told CNBC.