ABUJA: Nigeria's ailing president has broken a seven-week silence to insist he is getting better and plans to return to work but thousands marched regardless through Abuja on Tuesday to demand he step down.

Around 2,000 opposition supporters took to the streets of the capital demanding President Umaru Yar'Adua hand over power to his deputy to speed up electoral and constitutional reforms that have stalled during his lengthy absence.

Wearing white T-shirts emblazoned with the words "Enough is Enough", the protesters brandished placards demanding "Yar'Adua speak to us" and "What's happening to Yar'Adua?".

But speaking to the BBC -- by telephone -- Yar'Adua said he was recovering.

"At the moment I am undergoing treatment, and I'm getting better from the treatment," the BBC quoted him as saying from his hospital bed in Jeddah, Saudi Arabia.

"I hope that very soon there will be tremendous progress, which will allow me to get back home.

"As soon as my doctors discharge me, I will return to Nigeria to resume my duties.

The condition of 58-year-old leader has been the source of widespread speculation in Africa's second-largest oil exporter, and on Monday some online publications reported he had died the previous day.

But critics say his being alive, but absent, makes little difference to what they say is a dangerous power vacuum in Africa's most populous country, split between a Muslim-dominated north and Christian south and grappling with periodic outbreaks of religious violence.

"The issues are not simply about Yar'Adua being in the country or outside the country. The issues are numerous," Nobel laureate Wole Soyinka said as he addressed the rally.

"We challenge him on the continuing corrupt company that we see plotting around and controlling affairs from Aso Rock (presidential villa)," said Soyinka, who slammed "the insolence with which the legislators have treated this nation".

Parliament reconvened on Tuesday to discuss the political vacuum created by the absence of Yar'Adua, a northern Muslim. Related article: Nigerian lawmakers to visit president

Local media reports said the president of the senate was considering dispatching a team of investigators to Saudi Arabia to summon the president's personal doctor before the senate to verify his condition.

Yar'Adua did not delegate executive powers to his Vice President Goodluck Jonathan when he flew to Saudi Arabia on November 23 for hospital treatment. The law demands he does so in writing.

He has not been seen or heard since he was flown to Saudi Arabia to be treated for acute pericarditis, an inflammation of the membrane around the heart, and little detail of his condition has emerged.

The main opposition Action Congress said while happy to hear that the head of state is alive, it was disappointed that he chose a foreign media outlet to speak to his country which has been on edge for weeks.

"While we are happy that he is alive, that he spoke, we are disappointed that he chose the BBC to break his silence. It's quite shameful and a very big disrespect to Nigerians," AC spokesman Lai Mohamed told AFP.

"He has contempt for the local media and no respect for many Nigerians, many of whom have no access to the BBC," he said.

On what impact the telephone interview would have on concerns over a power vacuum in Africa's most populous country and second largest oil exporter, Mohamed said: "It changes very little".

"The fact that he is alive does not say anything about his state of health," said Mohamed.

Yar'Adua's voice sounded weak in the interview, the BBC said.

His absence has coincided with Nigeria being placed on a US terror watchlist after the failed attempt by a 23-year-old Nigerian, Umar Farouk Abdulmutallab, to blow up a US airliner on Christmas Day.

Yar'Adua expressed his gratitude for his nation's prayers for his recovery.

"I wish, at this stage, to thank all Nigerians for their prayers for my good health, and for their prayers for the nation."

Influential regional governors from Nigeria's 36 states met for several hours late Monday to early Tuesday but made no statement on Yar'Adua.