Douala (AFP) - Cameroon police on Saturday arrested around 50 supporters of opposition figure Maurice Kamto during an unauthorised march in Douala, his spokesman said.
"Mass arrests of activists (Mrs Michele Ndoki and around 50 others) and of supporters demonstrating peacefully today," the spokesman, Olivier Bibou-Nissack, said in a Facebook post, referring to one of Kamto's lawyers.
The protesters were arrested during a rally in Douala, the country's economic capital.
Among them was a journalist who was covering the event, sources said.
Kamto has rejected the official outcome of this month's presidential election, in which he was one of seven candidates seeking to unseat President Paul Biya who has ruled Cameroon for 35 years.
Kamto came second with 14.23 percent the vote, against 71.28 percent for 85-year-old Biya who has spent 35 years in power.
Ndoki is one of Kamto's lawyers who protested before the Constitutional Council against what she called "massive and systematic fraud" during the election.
Bibou-Nissack said the headquarters of Kamto's party, Movement for the Rebirth of Cameroon (MRC), had been vandalised.
The building was cordoned off by police who stopped anyone from approaching, an AFP journalist said.
On Friday, government minister Paul Atanga Nji warned that "any attempts to disturb the public order will be met with the greatest firmness".
Cameroon authorities were not available for comment Saturday afternoon.