ABUJA Nigerian President Umaru Yar'Adua returned under cover of darkness on Wednesday after three months of medical treatment in Saudi Arabia, reviving uncertainty over the leadership of Africa's most populous nation.
Vice President Goodluck Jonathan will continue to run affairs of state as Yar'Adua recuperates but the secrecy of his return raised concern that the 58-year-old leader's health will remain too frail for him to resume office.
"President Yar'Adua wishes to reassure all Nigerians that on account of their unceasing prayers and by the special grace of God, his health has greatly improved," Yar'Adua's spokesman Olusegun Adeniyi said in a statement.
But Yar'Adua was whisked by ambulance from Abuja airport in the early hours of Wednesday under tight security. There was no inspection of the presidential guard or formal reception by dignitaries as might be expected after such a long absence.
"The secrecy that shrouded his packaged return is a prima facie evidence that President Yar'Adua is incapable of exercising executive powers," the CNPP opposition grouping said.
"We demand to see our president."
Analysts say those close to Yar'Adua, including his powerful wife Turai, have grown concerned about Jonathan's assertive behavior since he assumed executive powers two weeks ago and wanted him back quickly, raising the prospect of a power tussle.
After a hurriedly summoned cabinet briefing, Information Minister Dora Akunyili said Jonathan had spoken to Yar'Adua's aides and would meet his wife later on Wednesday.
"When he is eventually briefed by our president, he will call us again," she said, giving no idea when that might be.
The return of Yar'Adua and his aides could limit Jonathan's room to address priorities he set out such as the amnesty for rebels in the oil-producing Niger Delta, improving power supplies, ensuring fair elections and fighting corruption.
"We hope that President Yar'Adua's return to Nigeria is not an effort by his senior advisers to upset Nigeria's stability and create renewed uncertainty in the democratic process," U.S. Assistant Secretary of State Johnnie Carson said in a statement.
Yar'Adua's absence brought sub-Saharan Africa's second biggest economy to the brink of constitutional crisis and threatened to paralyze the business of government.
"A mere press release won't solve his ability to rule," said Thompson Ayodele, Executive Director of the Lagos-based Initiative for Public Policy Analysis. "Nigerians would like to see him addressing them and be seen to be able to perform his required roles. Without that, he risks impeachment."
After taking over as Acting President, Jonathan adopted the mantle of leadership. Some politicians suggested he could run in polls due by April 2011 and have been positioning themselves for what one newspaper called a "post-Yar'Adua era."
Who gets the presidency is complicated by ethnic rivalries and many northerners believe Yar'Adua's largely Muslim north should keep the top position even if he can't stand. Jonathan is from the Niger Delta in the more heavily Christian south.
Militants said they sought more amnesty talks before deciding whether to reinstate a ceasefire they dropped during Yar'Adua's absence, threatening to renew attacks.
The cabinet has twice passed resolutions that there are no grounds to declare Yar'Adua unfit but splits have emerged between loyalists and ministers who feel he should step aside.
"Nigeria is an extraordinarily important country ... and all of those in positions of responsibility should put the health of the President and the best interests of the country and people of Nigeria above personal ambition or gain," Carson said.
Jonathan could in theory continue as acting president until the next elections, which could be brought forward to November.
But should Yar'Adua's condition be so serious as to render him incapable of holding office, he could step aside, allowing Jonathan to be sworn in as leader and name a new deputy.
Yar'Adua has been receiving treatment for pericarditis, an inflammation of the membrane surrounding the heart that can restrict normal beating, and also is known to suffer from a chronic kidney condition.
Many Nigerians were skeptical Yar'Adua would resume office.
"Seeing is believing. He's our president, he should appear on television. Let's wait and see," said civil servant Abolaji Habib, 49, in Lagos, Nigeria's biggest city.