Gabonese authorities imposed a curfew on Gabonese oil hub Port Gentil late on Thursday to counter violence sparked by the announcement that ruling party candidate Ali Ben Bongo had won Sunday's presidential election, Reuters reported.
Protesters targeted facilities owned by French oil major Total and U.S. oil services firm Schlumberger in the city, as well as former colonial power France's consulate there.
"The cabinet meeting asks instantly for a reinforcement of security measures across Gabonese territory," government spokesman Rene Ndemezoo Obiang said on national television.
Special security cells would be set up, he said, without giving details of what their powers would be, nor when the Port Gentil curfew would be lifted.
Opposition supporters clashed with security forces in the capital Libreville after Ali Ben Bongo, son of late President Omar Bongo, was declared winner of the poll with 47.1 percent of the vote, though the streets were deserted later in the day.
Ex-interior minister Andre Mba Obame received 25.9 percent of votes cast, and veteran opposition figure Pierre Mamboundou 25.2 percent.
Both had declared victory before the results were known and immediately rejected the outcome, but French Secretary of State for Cooperation Alain Joyandet said election observers had seen only minor irregularities.
"Observers who have given us their accounts have all said the election took place in acceptable conditions," he told RTL radio. "If the losing candidates want to contest the result, they should do so in the constitutional court," he said.
Ben Bongo's rivals have accused him of rigging the result to impose what they call a Bongo "monarchy" on the central African country.
Nearly 42 years of Omar Bongo's rule brought stability and prosperity to a volatile part of the continent, but not without accusations Bongo used petrodollars to enrich himself at the expense of the Gabonese people.
Observers and financial markets have played down the risk of major instability in Gabon -- a rare sub-Saharan country to have a Eurobond -- but a degree of short-term unrest in the immediate aftermath of the publication of results was expected given the breadth of opposition to Bongo.