Soldiers appeared on national television on December 7 to announce President Patrice Talon had been deposed but the attempted putsch was swiftly defeated by loyalist army forces with the help of the Nigerian air force and French special forces.

Several people were killed and the alleged coup leader lieutenant-colonel Pascal Tigri and other mutinous soldiers are still on the run.

On Monday, the around 30 accused appeared in front of a special prosecutor for the court for economic crimes and terrorism in the city of Cotonou, the sources said.

They were placed in pre-trial detention the following day at the end of their hearing, they added.

They are being prosecuted for "treason", "murder" and "endangering state security", the sources said.

A heavy security deployment could be seen around the court, an AFP journalist saw.

Separately, Chabi Yayi, son of former Beninese president and current opposition figure Thomas Boni Yayi, was released on Monday after being questioned but remains under prosecution in connection with the coup bid for reasons that are not known.

He is a member of the opposition party led by his father.

Although hailed for spurring economic growth, Talon is accused by critics of authoritarianism in a country once praised for its democratic dynamism.

He is due to hand over the reins of power in April after the maximum-allowed two terms leading Benin, which in recent years has been hit by jihadist violence in the north.