Nigeria's President Mr Olusegun Obasanjo, chairman of the African Union, branded as unconstitutional the army's appointment of a new Togo leader after the death of president Gnassingbe Eyadema yesterday.
A senior African Union official described the Togo events as a military coup.
"President Obasanjo will not accept any unconstitutional transition of power in Togo," said the Nigerian president's spokeswoman, Ms Remi Oyo.
"Speaking on behalf of the AU, President Obasanjo has urged the people of Togo to insist on respect of the constitution on the provision of an interim leadership that will lead to the democratic election of a new president for Togo," she said.
Shortly after the government announced Eyadema's death, Togo's army said it could not risk a power vacuum, sealed the West African country's borders and named his 39-year-old son president.
African Union Commission President and a former president of Mali, Mr Alpha Omar Konare, said it was a military coup.
Under Togo's constitution, the head of the national assembly, Mr Fambare Ouattara Natchaba, should have assumed power following Eyadema's death and elections organised within 60 days. The army said Mr Natchaba was not in Togo yesterday.