Rumours the president was critically ill and unable to return to the presidency have been swirling around Nigeria. His adviser Tanimu Yakubu Kurfi told the BBC the president’s enemies were behind the rumours.

Doctors said in December that President Yar’Adua was suffering from acute pericarditis, an inflammation of the lining of the heart. He is also known to have kidney problems.

Constitutional worries

Speaking by telephone to the BBC in an interview organised by the president’s office, Mr Yar’Adua said he was making a good recovery.

“At the moment I am undergoing treatment, and I’m getting better from the treatment. I hope that very soon there will be tremendous progress, which will allow me to get back home,” he said. He gave no indication of when he might return to Nigeria.

“I wish, at this stage, to thank all Nigerians for their prayers for my good health, and for their prayers for the nation.” He also wished the Nigerian national football team success in the Africa Cup of Nations currently under way in Angola. The BBC’s correspondent in Nigeria’s capital, Abuja, said the president’s voice had sounded weak.

President Yar’Adua’s silence until now and the fact he did not appoint Vice-President Goodluck Jonathan to serve in his absence have led to fears of a constitutional crisis.

There is a perceived danger of a power vacuum in a country that only saw the end of military rule just over 10 years ago, the BBC’s Will Ross reports from the capital, Abuja. There have also been complaints that important government business has been left hanging in the president’s absence.

‘Enough Is Enough’

Many Nigerians will be relieved to hear the president’s voice, says our correspondent, but calls to hand over power to the vice-president will continue.

UMARU YAR’ADUA

Born in 1951 in the northern Muslim state of Katsina

Self-confessed Marxist as an undergraduate

Became a chemistry teacher after university

Married twice, has nine children

Governor of Katsina from 1999 to 2007

During his governorship Katsina adopted Sharia law

Nicknamed “Baba-go-slow” since becoming president in 2007

High point of his presidency so far – the amnesty for oil militants

Has suffered from a chronic kidney condition for at least 10 years

There are three different court cases under way calling for power to be transferred to Mr Jonathan. Under the banner Enough Is Enough, an organisation called the Save Nigeria Group has called people on to the streets of Abuja.

The opposition plan is to march to the national assembly where senators are expected to be discussing the president’s health. Dozens of police, including riot police, have been deployed in Abuja ahead of the rally.

Prominent opposition politicians and lawyers, Nobel laureate Wole Soyinka and the Biafran secessionist leader, Chief Emeka Ojukwu, will be among the demonstrators. It is not clear if the demonstration will be well attended, our correspondent says.

Nigerians may be worried about their absent president but whether they will take time off to demonstrate is another matter, he adds.