General Mamady Doumbouya leads a junta that overthrew civilian president Alpha Conde in September 2021.

Under international pressure, the junta initially pledged to hold a constitutional referendum and hand power to elected civilians by the end of 2024 -- but neither has happened.

The general said in his New Year's speech that "in the first quarter of 2025, I will sign a decree setting the date" of the constitutional referendum.

"After the electoral code has been drawn up, during 2025, we will all work together to continue to lay the foundations for the general elections," he said.

Guinea's main opposition parties and civil society organisations have called for demonstrations in Conakry on January 6 to "demand the departure of the junta and the establishment of a civilian transition".

Since the junta took power, many opposition figures have been detained, brought before the courts or forced into exile.

Two former high-ranking officers and a doctor have died in unclear circumstances in recent months after their arrests.

A journalist from the Lerevelateur224 website was also arrested earlier this month by men in uniform in the suburbs of the capital, Conakry, and his whereabouts are unknown, his lawyers and a press union said.

The latest crackdown came last week when Aliou Bah, the leader of an opposition party, was arrested as he travelled to Sierra Leone with two colleagues for allegedly "insulting" the junta head.

His trial, which began Tuesday, is due to resume on January 2.