The Nigerian president has failed to appear at a cabinet meeting in the capital Abuja, after returning to the country from Saudi Arabia following three months of medical treatment.
Umara Yar'Adua's supporters had hoped he would show up at the meeting on Wednesday. The meeting, however, was chaired by Goodluck Jonathan, the vice-president, who is acting as the head of state.
Yar'Adua has not been seen or heard in public since his return on February 24, fuelling speculation that he is incapable of carrying out his job.
His silence has led many Nigerian newspapers to continue reporting that Yar'Adua is on a life support machine or in a coma.
There is also speculation that the president’s aides and family are holding him hostage in the presidential villa until they can figure out how to retain influence and power in the event of his death.
Al Jazeera's Yvonne Ndege, reporting from Abuja, said Yar'Adua's continuing absence had made it possible for Jonathan to consolidate his position.
"He has already received the backing of the United Kingdom, the United States, and on Monday the UN secretary-general Ban ki-moon sent him a message.
"He has also set up a presidential advisory committee again in an attempt to bolster his own position and his power within the cabinet."
Yar'Adua left Nigeria on November 23 to receive treatment for pericarditis, an inflammation of the membrane surrounding the heart that can restrict normal beating.
He is also known to suffer from a chronic kidney condition and has long been criticised for not being able to work more than five or six hours a day.
Aside from a political vacuum and near constitutional crisis, Yar'Adua's long absence had prompted street protests across the country, demanding his resignation.
It also threatened to paralyse the government until parliament installed Jonathan as acting head of state on February 9.
Nigeria's constitution says the president must make a written declaration that he is on vacation or unable to carry out his duties before a transfer of power could take place.
Yar'Adua had not officially given his consent to the transfer of power, but parliament said it based its decision on an interview that he gave the BBC last month, saying that he would return to work once his doctors gave him the go-ahead.
Source: Al Jazeera