Journalists protesting against the death of a Cameroonian newspaper editor clashed with riot police in the capital Yaounde.
Several hundred demonstrators were prevented from staging a sit-in at the Prime Minister's office to mark World Press Freedom Day.
The authorities said the protesters had not given them proper notice to hold a public rally.
Cameroon Expresseditor Bibi Ngota died last month in a Yaounde prison.
Banners with slogans
Some of the protesters carried banners with slogans such as "We are all Biby (sic) Ngota" and "Free all the journalists still in prison".
"I am enraged by such brutality when we wanted to hold a peaceful demonstration," said Polycarpe Essomba, a Cameroonian correspondent for Radio France Internationale (RFI).
"The police hit me with their clubs, I lost my jacket with my passport and money," he said, according to the AFP news agency.
Mr Ngota had been jailed on fraud charges.
His family rejects the government's explanation that he died of an HIV-related infection.
He was one of three journalists detained in March on charges of fraud and using false documents.
An adviser to the Cameroonian journalists' union (SNJC) said Mr Ngota was not given any medical treatment during his detention.
The New York-based Committee to Protect Journalists (CPJ) also said it held the authorities responsible for Mr Ngota's death.
Newspapers in Cameroon are subject to considerable official restrictions and tough libel legislation is in place.
In 2006 the media rights body Reporters Without Borders noted that: "Draconian laws regularly put journalists behind bars."