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, 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," stated a Nigerian newspaper NEXT said on its website.

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 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.

Decoy

Two planes arrived at the presidential wing of the Nnamdi Azikiwe international airport in Abuja, 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 maneuver when the president is traveling.

"He just landed at Abuja airport on a Saudi plane escorted by the presidential plane. He is on his way to the (presidential) villa now," one government source said.

Neither the government nor the presidency could be reached for comment. One presidency official said there was still uncertainty there about what the president's return from Saudi Arabia would mean.

Future

The political implications of Yar'Adua's will depend on the state of his health.

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 is also known to suffer from a chronic kidney condition.

Neither the presidency, nor the ruling party nor the cabinet has given any details on his health since shortly after he left, fuelling speculation about the gravity of his condition.