Abuja - Hundreds of Nigerians gathered in the capital Abuja on Wednesday for a march to the presidency to demand the appearance of ailing leader Umaru ar'Adua, two weeks after he returned from a Saudi hospital.

The 58-year-old leader has not been seen in public since being flown back after three months of treatment in Jeddah for a heart condition. There have been no announcements on his health but presidency sources say he remains in intensive care.

His return while still too frail to govern 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 Acting President Goodluck Jonathan.

A power struggle at the top of the OPEC member nation of 140 million people could bring paralysis in government decision-making, threatening an amnesty programme in the oil-producing Niger Delta and stalling momentum on reforms.

Several hundred people, many wearing T-shirts with "Save Nigeria Group" on the front and "Enough is Enough" on the back, gathered near to a city centre hotel under the watch of police officers lining the avenue.

Officials organising the march said they planned to walk to Aso Rock, the presidential villa, and hand a letter of protest to the Secretary to the Government of the Federation, who co-ordinates between the presidency and government ministries.