Ghana's president, John Atta Mills, has died at the age of 68.

The president's office says Mr. Mills died Tuesday at a military hospital in the capital, Accra. The statement says the president died a “sudden and untimely death,” a few hours after falling ill. The nature of his illness was not given.

President Mills had led Ghana since January 2009, after narrowly winning the 2008 presidential election. The election was hailed as a rare example of a peaceful transfer of power in Africa.

Ghana's constitution calls for Vice President John Dramani Mahama to be sworn in as Mr. Mills' replacement.