Thousands of Nigerians marched to the gates of the presidential villa Wednesday to demand an end to the presidency of ailing leader Umaru Yar'Adua so Acting President Goodluck Jonathan can take over as head of state. The 58-year-old leader has not been seen in public since he left for treatment in Saudi Arabia at the end of November. He was flown back to Nigeria two weeks ago but remains too frail to govern. Presidency sources say he is still in intensive care. His secretive return in the middle of the night raised fears that his inner circle of aides, led by his wife Turai, would fight to maintain their influence over Africa's most populous nation and seek to undermine Jonathan. A power struggle at the top of the OPEC member nation of 140 million people could bring paralysis in government, threaten an amnesty program in the oil-producing Niger Delta and cause reforms in sectors from banking to oil and gas to stall. A few thousand people, many wearing T-shirts with “Save Nigeria Group” on the front and “Enough is Enough” on the back, marched to within a few hundred meters of the presidential villa under the watch of unarmed police officers lining the streets. “We want the invisible president to be revoked. We are tired of a president we can't see, who can't govern. We want to see him,” Babatunde Ogala, a politician from the commercial capital Lagos and one of the protest organizers, told the rally. “If we can't see him we want someone else who is allowed to govern. Why is a cabal controlling our country,” he said. Jonathan sent Mahmud Yayale Ahmed, who as secretary to the government liaises between the presidency and ministries, to meet the protesters and collect a letter stating their demands. Tunde Bakare, a popular pastor and one of the leaders of the Save Nigeria Group, said the main ultimatum was an end to Yar'Adua's “invisible presidency” through an official declaration that he is incapable of holding office. Under the constitution, Jonathan would be sworn in as head of state and complete the unexpired presidential term, which runs to May next year, with a new vice president should Yar'Adua be formally declared too sick to govern, resign or die.