Gabonese former member of parliament Bertrand Zibi Abeghe was sentenced on Tuesday to six years in jail for his part in post-electoral violence, one of his lawyers told AFP.
Libreville Criminal Court convicted Zibi on charges of "violence and assault" and "illegal possession of a firearm", lawyer Charles-Henri Gey said by telephone.
But he was acquitted of "instigating actions... (meant) to stir up trouble or demonstrations against the authority of the state" and of failure to assist a person in danger.
"We are going to appeal against this decision of justice, we will fight on until Mr Zibi's innocence is recognised by the judges," said Gey.
Zibi's trial opened at the beginning of July, almost three years after his arrest. The public prosecutor called on the court to jail him for 10 years.
Zibi caused an uproar when he quit his post as an MP in the ruling Gabonese Democratic Party (PDG) during a public meeting attended by President Ali Bongo Ondimba in July 2016.
His resignation came a month before a presidential election in which Bongo was re-elected.
Bongo first took power in the oil-rich equatorial African state in 2009, the elected successor to his father Omar Bongo, who ruled Gabon from 1967 until his death.
Seven years later, Ali Bongo won a second term in a hotly disputed presidential poll where he was challenged by Jean Ping, known for his previous diplomatic roles in the African Union and at the United Nations.
Zibi was arrested at Ping's campaign headquarters on August 31, 2016, as violence erupted following the announcement of Bongo's electoral victory.
Hundreds of people were detained during street protests and as the National Assembly was set on fire. The security forces launched an assault on Ping's operational base.
The government reported three deaths in the wave of violence, while opposition and civil society sources said they had identified 30 people killed, while others went missing.
Late in October 2018, Ali Bongo suffered a stroke and spent weeks in a hospital in Riyadh before being moved to Morocco, a longtime ally of Gabon. An apparent coup bid early this year was foiled.