Guinean special forces on Sunday announced the arrest of President Alpha Condé in a statement broadcast on state TV as uncertainty gripped the West African nation amid reports of heavy gunfire around the presidential palace in the capital, Conakry.
In a short broadcast on state TV, soldiers who staged an uprising said they have dissolved the constitution and the government in the West African state.
However, the defence ministry said an attack on the presidential palace by mutinous forces had been put down.
Heavy gunfire had broken out near the presidential palace in Conakry on Sunday morning, with several sources saying an elite national army unit led by a former French legionnaire, Mamady Doumbouya, was behind the unrest.
An unidentified soldier, draped in Guinea's national flag and surrounded by eight other armed soldiers, said in the broadcast that they planned to form a transitional government and would give further details later.
The soldier spoke after videos shared on social media - which could not be immediately authenticated - showed Conde surrounded in a room by army special forces.
The defence ministry said the attempted insurgency had been put down.
"The presidential guard, supported by the loyalist and republican defence and security forces, contained the threat and repelled the group of assailants," it said in a statement.
"Security and combing operations are continuing to restore order and peace."
Earlier, videos shared on social media showed military vehicles patrolling Conkary's streets and one military source said the only bridge connecting the mainland to the Kaloum neighbourhood, which houses the palace and most government ministries, had been sealed off.
Many soldiers, some heavily armed, were posted around the palace, the source added.
Three witnesses told Reuters they saw two civilians with gunshot wounds.
"I see groups of soldiers heading towards the presidency. There has been a lot of shooting," said Ousmane Camara, a resident of Kaloum.
A Reuters reporter saw two convoys of armoured vehicles and pick-up trucks heading towards Conakry Autonomous Port, also near the palace. The convoy was accompanied by a white vehicle that appeared to be an ambulance.
Conde won a controversial third term in October after changing the constitution to allow him to stand again despite violent protests from the opposition, raising concerns of a backslide in a region that has seen coups in Mali and Chad in recent months. Footage shared on social media, which Reuters was not immediately able to verify, showed heavy gunfire ringing out over Conakry, and vehicles full of soldiers approaching the central bank, close to the palace.
"President Alpha Conde is doing extremely well... the situation is under control," an ally of the president said in a video shared on WhatsApp.
Guinea has seen sustained economic growth during Conde's decade in power thanks to its bauxite, iron ore, gold and diamond wealth, but few of its citizens have seen the benefits.
Critics say the government has used restrictive criminal laws to discourage dissent, while ethnic divisions and endemic graft have sharpened political rivalries.