Anti-graft groups have alleged that the "unceremonious" suspension of Magu as acting chairman of EFCC may roll back the momentous gains already recorded under his tenure.
The groups, in a joint letter to President Muhammadu Buhari, dated July 9, said Magu might be a pawn in the desperate attempts by corrupt officials to kill the EFCC or turn it into a willing tool of corrupt politicians.
The letter was signed by Lucas Manes of Re: Common, Nicholas Hildyard of Corner House, Simon Taylor of Globalwitness - all European organisations - and Olanrewaju Suraju of the HEDA in Nigeria.
"What is going on in Nigeria is of concern to the international community. Mr Magu has proved himself to be up to the task. His determination to fight corruption is evident by the recovery of stolen funds and properties plus his own high moral ground earned at the cost of diligence and hard work never before seen," they said in the letter.
The groups said they were alarmed over Magu's suspension, noting that his "political" removal questioned Nigeria's will to deal with a major cause of the country's underdevelopment which is corruption.
They, however, said the international community was not opposed to Magu being investigated since all allegations of corruption must be thoroughly probed.
They said they were constrained to speak because due process and proper disciplinary procedures have not been followed.
"The procedures are clearly being hijacked by detractors of Magu in the political space and this is eroding the potential credibility of the outcome of the panel constituted to probe these allegations. The hounding of Magu through seemingly politically connected sponsored media harassment only makes matters worse", they said.
They said Magu's EFCC was "completely different from the sclerotic, timid, politically captured bureaucracy that it was in the previous period."
"The credit for this is due in large part to you for appointing Magu and sticking with him despite efforts to unseat him," the groups stated in the letter to Buhari.