At least two people were injured as heavy gunfire broke out near the presidential palace in Guinea's capital Conakry on Sunday morning, while military vehicles patrolled the streets, witnesses said and videos shared on social media showed.
It was not clear who was exchanging fire.
A senior government official said 83-year-old President Alpha Conde was unharmed but gave no further details.
A military source said the gunfire involved angry members of the Special Forces, an elite army corps. The source did not say what caused the anger.
Another military source said the only bridge connecting the mainland to the Kaloum neighbourhood, which houses most of the ministries and the presidential palace, had been sealed off and many soldiers, some heavily armed, were posted around the palace.
"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.
