Nigeria's acting leader will run state affairs while President Umaru Yar'Adua recovers after three months' medical treatment abroad, the presidency says. The 58-year-old's surprise return from Saudi Arabia comes two weeks after Vice-President Goodluck Jonathan took over, amid fears of a power vacuum. Mr Yar'Adua's condition is unknown - he has not been seen in public and it is unclear when he could resume office. His plane from Jeddah was met at Abuja by an ambulance in the early hours. "President Yar'Adua wishes to re-assure all Nigerians that on account of their unceasing prayers and by the special grace of God, his health has greatly improved," the president's spokesman, Olusegun Adeniyi, said in a statement. "However, while the president completes his recuperation, Vice-President Jonathan will continue to oversee the affairs of state," it added. Acting President Jonathan postponed a weekly cabinet meeting on Wednesday, telling ministers he would hold a special briefing at 1400 (1300 GMT). President Yar'Adua has not been seen in public since flying to Jeddah last November to be treated for pericarditis, an inflammation of the membrane protecting the heart. Analysts say there has been considerable jostling for power behind the scenes as politicians look ahead to elections due by April next year. In Mr Yar'Adua's absence, acting President Jonathan has been reshuffling ministers, pledging to tackle power shortages and forging ahead with an amnesty for militants in the oil-rich Niger Delta. The amnesty was seen as Mr Yar'Adua's major achievement since coming to power in 2007, but it had been jeopardised by his absence. Source: BBC