Lagos - Muhammadu Buhari was elected as Nigeria's president on a promise to root out rampant corruption in government that has seen billions of dollars of public money stolen over decades.But since his landmark election win in 2015 he has yet to secure a high-profile conviction for graft while the main opposition accuse him of mounting a political witch-hunt.Now, a growing scandal involving an indicted civil servant has engulfed the presidency, giving Buhari's detractors fresh ammunition and raising questions about his grip on power.Last weekend, the Economic and Financial Crimes Commission (EFCC) announced that the interior ministry had reappointed Abdulrasheed Maina to the civil service.Maina headed a task force on pension reforms during the last administration but fled Nigeria in 2015 after claims he stole $5.6m.An Interpol arrest warrant was issued yet he still managed to return to Nigeria, where he has apparently since enjoyed armed police protection.Buhari, who it has been claimed knew about Maina's return, responded by ordering Maina's dismissal and arrest but the EFCC said he had again fled Nigeria to avoid being picked up.The opposition Peoples Democratic Party (PDP) has predictably seized on the affair, claiming it showed the government's fight against corruption to be "mere propaganda".Ayodele Fayose, the PDP governor of Ekiti state who is eyeing the party's presidential ticket in 2019, jumped on his favourite target - Buhari himself."Fellow Nigerians, are you now convinced that Buhari's anti-corruption fight is like Satan calling Judas Iscariot a sinner?" he wrote on Twitter. Grip on power Buhari, 74, has spent much of this year in London being treated for an unspecified illness that has seen him undergo blood transfusions and a barrage of tests.He returned to Nigeria in August after months of speculation that he was seriously ill and rumours of a power struggle to succeed him if he were to step down or even die.For Clement Nwankwo, of the Policy and Legal Advocacy Centre in Abuja, "the bigger question (about the Maina affair) is how much control does the president have over his government"."Is he fully aware of what is going on?"Nwankwo said he was "worried that some people in the presidency would have the audacity to smuggle Maina... and even promote him without the president's knowledge".He pointed to hints from the president's wife, Aisha, and one of his daughters, Zahra, about behind-the-scenes machinations and unchecked corruption at the heart of the presidency.In a Facebook post in July, Aisha Buhari alluded to "hyenas" and "jackals" surrounding the president, while Zahra called for an investigation of the presidential health facility.The State House Clinic, which receives massive government funding every year, lacked basic drugs and equipment, she said last month, adding: "Where is the money going to?"The two women's aims in speaking out appeared to be "to simply ask Nigerians for help", said Nwankwo. 'Tainted' credentials? Even before the Maina scandal, Buhari was facing criticism for allegedly sitting on a report into claims of graft by Nigeria's top civil servant and the intelligence agency chief.The report, into an alleged kickback scheme involving aid money for victims of Boko Haram and the discovery of $43m in cash at a Lagos apartment, was submitted in August.Debo Adeniran, from the Centre for Anti-Corruption and Open Leadership lobby group, said the Maina case was "a big embarrassment and shame to Nigeria"."It shows that there are people in Buhari's administration that are not committed to his ideals concerning the anti-corruption war," he said."By recalling Maina to the civil service after being implicated in a pension scam, this regime has put a big question mark on the president's integrity."Buhari's much-publicised anti-corruption credentials have been tainted. It shows that he is the only one who believes in the crusade."It has long been suspected that not everyone in government shared Buhari's anti-corruption zeal but leading lawyer Femi Falana said the situation could still be salvaged.Maina should be located, charged and put on trial alongside anyone who helped him, he said."Those who recalled and promoted the fugitive ought to be sanctioned by President Buhari to serve as a deterrent to others who may wish to sabotage the war against corruption." But while Buhari should be given credit for ordering an investigation, "follow-up action" was essential to show the public how serious his government is about tackling the issue.