Several people have been injured in Guinea's capital, Conakry, in clashes between government and opposition supporters.
There are also reports that one person was killed in the violence when protesters blocked the main bridge and barricaded the main roads.
The two groups are split along ethnic lines, and the disturbance led to ethnic riots at the central market.
There is tension in the country over delayed parliamentary elections.
In 2010 the West African state held its first democratic election since independence from France in 1958.
Alpha Conde, from the Malinke ethnic group, won the presidency after half a century in opposition.
But tensions with his bitter opposition rivals, who mainly come from the Peul ethnic group - also known as the Fula - have not eased since the election.
On Thursday, there was a big opposition rally calling for the departure of the South African company, hired by the government to re-do the electoral roll, over fears it could be influenced by the ruling party.
The country has had a turbulent few years: A military junta took over in December 2008 following the death of President Lansana Conte, who had himself seized power in a coup 24 years earlier.
Following the attempted assassination of the putsch leader, Capt Dadis Camara, a provisional government eventually supervised the transition to civilian rule.
Despite being the world's main exporter of the aluminium ore bauxite, Guinea is one of Africa's poorest countries.