Opposition supporters in Gabon have set fire to the embassy of Benin and burnt cars in the streets of the capital Libreville.
Reports say the violence came after the announcement of the death of senior opposition figure Andre Mba Obame.
The 57-year-old died after a prolonged illness in neighbouring Cameroon earlier on Sunday.
Mr Obame refused to accept defeat in elections in 2009 and declared himself president.
The former advisor to long-time President Omar Bongo lost that election to the president's son Ali Bongo.
But Mr Obame said that he was the rightful winner and legitimate president.
His National Union (NU) party was dissolved by the government as a result, and Mr Obame was accused of treason.
The ban on the NU party was lifted in February.
The NU announced Mr Obame's death in the Cameroonian capital Yaounde but did not give a cause of death.
Some of his supporters have accused the government of murdering Mr Obame.
"I think that the Gabonese people know that they've lost the true president elected in 2009 in unclear conditions," National Union spokesman François Ondo Edou told Reuters.
Gabon's Interior Minister Guy Bertrand Mapangou said that everything would be done to find the perpetrators of the violence.