Guinean protesters thronged the streets of the capital Conakry on Tuesday in fresh protests against embattled President Alpha Conde.
The crowds, most wearing opposition T-shirts, formed a sea of red -- the colour of the opposition -- with lawmaker Fode Oussou Fofana estimating their numbers at "more than a million".
AFP could not independently verify the figure.
Protesters carried placards reading "No to dictatorship," "Death to murderers" and "Free the heroes".
The poor West African country of some 13 million has seen rolling demonstrations since last month over suspicions that the 81-year-old president is manoeuvring to seek a third term in office.
At least 20 civilians have been killed since mid-October and one gendarme has also been killed.
A Guinean court handed down jail terms to several opposition leaders in October.
On Tuesday, opposition leader Cellou Dalein Diallo could be seen in the middle of the crowd on the hood of a 4x4 vehicle.
Leading civil society members including a top lawyer and a former defence minister took part in the protest.
Schools and shops were shut across much of capital, and security officers were out in force, although they maintained a low profile, an AFP journalist said.
Conde, whose second term ends next year, launched constitutional consultations in September, saying the former French colony's basic law "concentrates corporate interests" and needed reform.
But his adversaries say the president will try to push through an amendment allowing him to seek a third term in elections due in 2020. He has neither confirmed nor denied his intentions.