A federal court in Nigeria's capital, Abuja, will hold hearings this week on three lawsuits seeking to compel ailing President Umaru Yar'Adua to transfer powers to Vice President Goodluck Jonathan. The parliament also plans to discuss the president's illness when it resumes this week.
The Nigerian Bar Association, a prominent human rights lawyer and a former lawmaker have filed separate suits seeking recognition for Vice President Goodluck Jonathan as acting president, given Mr.Yar'Adua's six-week absence because of ill health.
Nigeria's constitution states the president should write to both houses of parliament if he is leaving on holidays or otherwise unable to govern, and that the vice president should take over until he writes to the contrary.
The 58-year-old leader was flown to a clinic in Saudi Arabia in late November without formally notifying the parliament. Nigeria Bar Association President Rotimi Akeredolu says the group is wants to resolve the current leadership crisis.
"There is no other body that should be more concerned than the Nigerian Bar Association about constitutionality and that is why we are in court," he said. "We are in court to see that our constitution is obeyed to the letters."
The government is facing growing pressure to provide concrete evidence that Mr.Yar'Adua is fit enough to govern Africa's most populous nation.
Officials have said the president is responding to treatment for a heart condition, and does not suffer from an infirmity that would render him permanently incapable of discharging his functions.
Information minister Dora Akunyili told reporters Vice President Jonathan informed a cabinet meeting last week that he had a telephone conversation with President Yar'Adua.
"The vice president told us in council that he spoke with Mr. President briefly at about 8 pm, yesterday," he said. "This is the only information I have."
But critics say government assurances are not enough and that further disclosure about Mr.Yar'Adua's health was needed.
Some political analysts warn the Nigerian president's death or even a further deterioration of his health could lead to instability.