Supporters of Gabon opposition candidate Jean Ping have clashed with security forces after President Ali Bongo was declared the winner of Saturday's presidential election.
Mr Bongo secured a second seven-year term with 49.8% of the vote to Mr Ping's 48.2 %, a margin of 5,594 votes.
Mr Ping disputes the result. His camp has said figures from the president's stronghold showed a 99% turnout.
In 2009, the Mr Bongo took over from his father, who came to power in 1967.
Security forces fired teargas to disperse supporters of Mr Ping who were trying to access the electoral commission headquarters in Gabon's capital, Libreville.
Blanche Simonny, a Jean Ping supporter and member of the civil society group Ca Suffit Comme Ca (Enough is Enough), told BBC Focus on Africa that thousands of people had gathered at the opposition headquarters in Libreville before starting the march to the electoral commission.
She said smoke was billowing from burnt tyres left on the streets.
There was no independent statement from the electoral commission (Cenap), after Interior Minister Pacome Moubelet-Boubeya announced the results.
Delegates representing the opposition in Cenap walked out of the vote count and refused to sign papers validating Mr Bongo's victory, according to a BBC Afrique reporter in Libreville.
Before entering politics Mr Ping was a renowned career diplomat who served as the chairman of the African Union Commission.