Update: Nigeria’s President Umaru Yar'Adua quashed mounting rumors that he had died by giving a brief phone interview early Tuesday to the BBC.

“At the moment I am undergoing treatment, and I am getting better from the treatment. I hope that very soon there will be tremendous progress, which will allow me to get back home," said Yar’Adua.

But the president’s halting sentences in a quavery voice offered little real reassurance about his health. Nigerian opposition parties have in recent weeks said that only up-to-date video footage of the president can restore public confidence that he is healthy enough to remain in office.

Public demands for a formal handover of power to Vice President Goodluck Jonathan are reaching fever pitch in Nigeria this week as parliament resumes work after its holiday recess.

Several prominent Nigerians, including Nobel laureate Wole Soyinka, are due to lead a protest march Tuesday through Abuja, Nigeria's capital. A series of lawsuits calling for a handover to Jonathan are also due to be heard this week.

ABUJA, Nigeria — Nigerians are asking where is their president?

The absence and silence of President Umaru Yar'Adua for more than 50 days has left Nigeria without effective leadership as the country grapples with being placed on a security watch-list, following a young Nigerian's alleged attempt to bomb a U.S. bound airplane on Dec. 25.

Many Nigerians have called the new security-risk status unfair and view it as part of a wider decline in ties between the U.S. and its fifth-largest oil supplier. Experts reason that the fact that president Yar'Adua has not been seen for nearly two months, since going to Saudi Arabia for medical treatment in November, may be part of the reason that the U.S. views Nigeria as a potential security risk.

Washington announced earlier this month that it would impose extra security checks on passengers traveling to the U.S. from 14 countries, including Yemen, Somalia and Nigeria. The list is a response to the alleged attempt by Umar Farouk Abdulmutallab, a 23-year-old Nigerian, to set off an explosive on Northwest Airlines flight 253 to Detroit.

From government ministers to taxi drivers, Nigerians are outraged by the classification. Many argue that Abdulmutallab was Nigerian “in name only.” The son of a prominent banker had spent a large part of the past decade abroad, being educated in Togo, the U.K. and the Middle East. He is widely thought to have been recruited by Al Qaeda in the U.K. or Yemen.

“It is unfair to discriminate against over 150 million people because of the behavior of one person,” Dora Akunyili, Nigeria’s information and communications minister, told reporters. “Abdulmutallab was a well-behaved child from a responsible family who developed the ugly tendency to do what he tried to do because of the exposure outside the shores of Nigeria.”

In Abuja, Nigeria’s capital, young people on national service have started wearing patriotic T-shirts in the country’s official colours of green and white. The t-shirts bear the slogan “Proudly Nigerian” on the front and “Not a terrorist nation” on the back.

Africa’s most populous country with about 150 million people is roughly divided into the Muslim north, with about 50 percent of the population, and a Christian south, with about 40 percent of the people. The country's lucrative oil and banking industries are concentrated in the south. Muslim sects in the north, where employment rates and economic growth are especially low, have in recent months clashed violently with security forces. However, these homegrown groups have no proven links with international terrorist movements.

Some warn that attempts to deter potential terrorists by placing Nigeria on the U.S. watch-list might only serve to stoke anti-West feelings among certain sects.

“The decision was hasty ... it will just compound the idea that the U.S. is anti-Islam,” said Hussaini Abdu, an Abuja-based activist who has written several research papers on Nigeria’s Muslim sects. “The U.S. should have instead tried to engage with the Nigerian government and understand the nuances of what is happening here.”

Following public euphoria at the appointment of the first black U.S. president, Nigerians have been disappointed by Barack Obama’s lack of special attention. Obama pointedly chose to visit nearby Ghana, often lauded as stable and well-governed, rather than Nigeria on his first presidential trip to Africa last July. In a further blow, Hillary Clinton, secretary of state, rebuked Nigeria on its lack of transparency when she visited Abuja in August.

As a diplomatic storm grows around the Abdulmutallab case, Nigeria also remains without a leader to defend the country and speak on its behalf. Umaru Yar’Adua, the president, who has a history of medical problems, has left the country adrift. Nigerians have neither seen nor heard from the president since his abrupt departure in November.

“If the president had been around, he could have spoken to Mr. Obama [about the list] on a level — as colleagues,” said Emmanuel Onwobiko of the Human Rights Writers Association, a lobby group that has demanded that parliament compel Yar’Adua to confirm his whereabouts and the state of his health. “But nobody is in charge.”

Sub-Saharan Africa’s top oil producer has edged ever further to the brink of a constitutional crisis in recent weeks, as lawyers and activists say the president must at least temporarily hand over to Goodluck Jonathan, his deputy.

Opposition parties are demanding a Fidel Castro-style video statement, live from the presidential sickbed, just to prove that Yar’Adua is still alive. Meanwhile, members of the ruling People’s Democratic Party are furiously plotting for the post-Yar’Adua succession battle.

Such instability at a crucial time could well have been on the minds of those who drew up the U.S. watch-list, experts say.

“I think Yar’Adua’s absence was a big part of America’s decision,” said Rolake Akinola, a West Africa analyst at Control Risks, a consultancy. “The fact that Abdulmutallab was Nigerian was largely incidental ... and it is wrong to say that Nigeria is a breeding ground for terrorists. But the lack of a leader casts doubt on the country’s ability to respond to any kind of crisis, be it a terrorist event or anything else.”