Renegade Mali soldiers seized control of the presidential palace on Thursday through an overnight coup bid against President Amadou Toumani Toure.
Rebel soldiers made the announcement through state television which they captured and took off the air for several hours on Wednesday.
A group of soldiers who appeared on state television early on Thursday identified themselves as the Committee for Re-establishment of Democracy and Restoration of the State.
A nationwide curfew has been imposed and the constitution suspended. The whereabouts of the president and other members of the government remain unknown.
The soldiers were unhappy with the way the Toure government has handled a rebellion and lack of better weapons to fight insurgents.
Ethnic Tuareg fighters have recently advanced in the northern districts as they are fighting to create a separate desert homeland in Mali's north.
The Tuareg-led rebellion has killed a number of people and forced at least 200,000 civilians to flee their homes.
The latest events were triggered by a visit by the defence minister to the army barracks in the town of Kati, north of Bamako.
The talks with the minister took an unexpected turn when the soldiers started throwing rocks at the minister and began shooting in the air, accusing him of betraying them.
"We now know it is a coup d'etat that they are attempting," Reuters quoted a defence ministry official who confirmed the clashes at the presidential palace earlier.