Guinea President Lansana Conte has failed to make his usual independence day speech, increasing concern that his health is continuing to deteriorate.
President Conte won a third term in 2003 elections despite poor health
Mr Conte, who seized power in a coup 22 years ago, suffers from acute diabetes and is also thought to have leukaemia.
He twice flew to Switzerland for treatment earlier this year.
A BBC correspondent in the region says many Guineans now see Presidential Affairs Minister Fode Bangoura as the real power in their country.
In the absence of the president, Mr Bangoura laid flowers at a monument to national martyrs on Monday, 48 years after Guinea gained independence from France.
Guinea's opposition says Mr Bangoura has in effect taken over the running of the country with President Conte too sick to take much of an active role.
The government has frequently denied this, but the charge is widely believed by foreign diplomats and Guineans alike.
The BBC's James Copnall says President Conte's unexpected silence will reinforce suspicions that his health is in a very poor state indeed.
Our correspondent says Guinea is suffering too.
There have been two general strikes this year, as the economy is in ruins and people are finding it harder and harder to earn enough money to survive.