The president travelled to Saudi Arabia in November last year where he was treated for acute pericarditis and though he returned to Nigeria on February 24, he has not been seen in public.

Leadership crisis

"It had been rumoured that acting president Goodluck Jonathan would get rid of Yar'Adua's ministers, remember the cabinet had all been appointed by the president," Yvonne Ndege, Al Jazeera's correspondent in Abuja, the Nigerian capital, said.

In depth

  Profile: Umaru Yar'Adua
  Profile: Goodluck Jonathan
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"This is a signal for many that Goodluck Jonathan is perhaps about to put in place his own men, his own women, his own team.

"It was felt by many Nigerians that the cabinet was basically packed to the rafters with Yar'Adua loyalists who weren't doing the job they were supposed to be doing, or rather doing a good enough job."

Yar'Adua's absence has caused a near constitutional crisis in Nigeria, with protests held in the capital demanding he step aside.

The president's supporters have also held rallies in his favour.

Balancing act

Jonathan's acting presidency has been controversial in Nigeria as the presidency reflects a regional balancing act between the Muslim north and the Christian south.

The role traditionally switches between the two sides with every election.

Yar'Adua is a Muslim from the north while Jonathan is a Christian from the south, leaving many of Yar'Adua's supporters unhappy that their candidate has not seen a full term in power.

The political turmoil has come at a time when central Nigeria has been hit by ethnic and religious violence.

Hundreds of people have been killed in several clashes between Muslim herdsmen and Christian villagers around the city of Jos.