Leaders of an opposition coalition in Guinea were arrested on Saturday, just two days before planned demonstrations against a possible attempt by President Alpha Conde to seek a controversial third term.
The National Front for the Defence of the Constitution (FNDC), which was formed in April by the main opposition parties, civil society associations and trade unions, is calling for protests on Monday.
Masked members of Guinea's security forces detained the FNDC's coordinator Abdourahamane Sanoh, and other top members of the umbrella grouping, said an opposition leader Cellou Dalein Diallo.
Last month Conde, 81, called on the public to prepare for a referendum and elections, stirring talk that he was planning to overcome a constitutional ban on a third term in office
The FNDC has called for a general strike and protests on Monday throughout the country.
Conde has attracted criticism over the police's deadly use of gunfire to quell demonstrations. About 100 people have been killed since he came to power in 2010, according to the opposition.