According to Reuters, which cited a defence lawyer, the sentence was handed down on Friday, May 25, 2018.
President Paul Biya's predominantly Francophone government had arrested Mancho Bibixy, a radio presenter in the English-speaking Northwest Region, and several other activists in 2017 as part of a crackdown on a developing Anglophone secessionist movement.
Bibixy's lawyer, Claude Assira, who told Reuters that one activist was acquitted, said the convictions "would only worsen the ... Anglophone crisis".
In 2016, teachers and lawyers had started a peaceful protest movement against the perceived marginalisation of the English-speaking minority but it became a full-blown crisis the following year after the government launched violent crackdowns on the protesters.
The intimidation and suppression fuelled support for radical separatist movements, including armed groups aiming to create an independent state that has killed over 20 soldiers and police officers.
The violence has unsettled the Central African oil producer months ahead of an election in which the country's President Biya will seek to extend his 35-year rule.