Guinea's Presidency declared a week of mourning for those killed after what it described as a "tragic drama".
A statement from the office of President Alpha Conde said the incident happened at a beach in the Ratoma neighbourhood of the capital Conakry.
It added: "While waiting for the results of an investigation, information from health and security authorities indicate deaths and several injuries."
An investigation has been launched to determine what caused the stampede. The official in charge of organising the concert was suspended.
The stampede, which happened during celebrations to mark the end of the holy fasting month of Ramadan in mainly Muslim Guinea, comes at a time when health workers are already stretched by an outbreak of Ebola.
The deadly tropical virus was first detected in the West African country in February and has since spread to Liberia and Sierra Leone.