Shortly after the announcement that Gnassingbe Eyadema was dead, the armed forces chief of staff said on state media in Lome that 39-year-old Equipments and Postal Services Minister Faure Eyadema was Togo's new leader. He said the armed forces had been confronted with what he called a power vacuum.
Under the constitution, the parliament speaker is supposed to take over, but the army chief of staff said he is out of the country.
Land, sea and air borders have been closed until further notice.
The earlier statement concerning Mr. Eyadema's death said he had died earlier in the day, while he was being evacuated for treatment. It also appealed for calm and said Togolese should avoid descending into chaos and anarchy.
The main opposition leader, whose father was deposed in a coup organized by Mr. Eyadema in 1963, Gilchrist Olympio, called the day's development a coup. "It is a coup because according to our constitution if the president is incapacitated it is the speaker of the house who takes over. Now, they've gone and appointed a son, an unknown son, of the president to take over," he said. "So far, as we are concerned, we are not out of the woods yet, because we are fighting to put in place a democratic structure in the country."
Mr. Olympio was barred from the most recent presidential election in 2003, which was marred by fraud and intimidation.
The late Mr. Eyadema, who was 69, was last seen outside Togo attending the African Union summit in Nigeria last month, looking sickly.
He organized a second coup in 1967 to formally assume power which he held on to nearly 38 years despite assassination attempts, a plane crash and calls for more democracy.
News reports from Togo said the streets of the capital Lome were quiet late Saturday after the announcement that Mr. Eyadema's son was the new leader. This could not be confirmed immediately, as phone lines into Togo apparently were cut off.