Nigerian President Umaru Yar'Adua arrived back in Abuja on today after three months in a Saudi Arabian hospital, renewing uncertainty over the leadership of Africa's most populous nation.
There was no immediate word on his condition but a presidential adviser said it was unlikely he would immediately resume office, suggesting Vice President Goodluck Jonathan would remain acting head of state for now.
Yar'Adua's absence brought sub-Saharan Africa's second biggest economy to the brink of constitutional crisis and threatened to paralyse the business of government, until Jonathan was sworn in as acting leader two weeks ago.
Jonathan has since adopted the mantle of leadership, reshuffling ministers, pledging to tackle chronic power shortages and forge ahead with an amnesty in the oil-producing Niger Delta. Some politicians have said he could win support to run for president in elections due by April next year.
"The news of the president's arrival is reportedly causing a lot of anxiety in Abuja especially among politicians, many of whom had prepared themselves for a post Yar'Adua era," Nigerian newspaper NEXT said on its website.
Emmanuel Egbogah, presidential adviser on petroleum matters, confirmed Yar'Adua had arrived in Nigeria this morning but told Reuters it was "doubtful" he would immediately take over executive powers.
Information Minister Dora Akunyili had no immediate comment.
"I heard about it this morning and I am yet to be briefed," she told Reuters.
Analysts say those close to Yar'Adua were growing concerned about Jonathan's assertive behaviour after the Senate and House of Representatives recognised him as acting head of state two weeks ago and wanted to bring the president back quickly.
A Senate resolution passed on Feb. 9 stated that Jonathan would cease to be acting president once Yar'Adua stated in writing to the leaders of both houses of parliament that he has returned from "medical vacation".
But Nigeria's politicians have been flexible in their reading of the constitution during the crisis.
"The Senate resolution was very clear. It says the acting presidency lapses once the president sets foot on the shores of Nigeria," a government source close to Yar'Adua said.
"We now have a president and a vice president. The president can choose to delegate or carry out his functions directly."
The cabinet, which has twice passed resolutions that there are no grounds to declare Yar'Adua unfit to govern, is due to hold a weekly meeting later on Wednesday.
Splits have emerged between Yar'Adua loyalists and ministers who feel he should step aside. Any new pronouncements after Wednesday's meeting could be key to his political fate.
Many Nigerians remained sceptical he 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.
Yar'Adua arrival was shrouded in secrecy.
Two planes arrived at the presidential wing of the Nnamdi Azikiwe international airport in Abuja in the early hours of Wednesday, one of them met by an ambulance which left under a heavy police escort shortly afterwards, a Reuters witness said.
Soldiers lined the main road from the airport to the city, a standard manoeuvre when the president is travelling.
Jonathan could continue as acting president until such time as Yar'Adua's health recovers and he is fit enough to resume office. Should his 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.
Neither the presidency, the ruling party nor the cabinet have given any details on his health since shortly after he left, fuelling speculation about the gravity of his condition.
"The state of his health is very important for the unfolding political dynamics ... It's almost impossible to keep such information secret now he is back," said Kayode Akindele, a director at Lagos-based Greengate Strategic Partners.