* Sporadic clashes overnight in Port Gentil
* Heavy security presence in city - resident
* Shops looted in post-election riots
LIBREVILLE, Sept 6 (Reuters) - Security forces clashed with gangs of protesters in Gabon’s oil hub Port Gentil overnight in a third day of unrest since a disputed presidential election brought the son of the late leader to power, a resident said.
Port Gentil has seen the brunt of violence since Ali Ben Bongo, son of long-time ruler Omar Bongo, was declared winner of last Sunday’s poll, with widespread looting and attacks targeting the interests of ex-colonial power France.
"During the night it was groups of five to six people. Security forces would disperse them and they would melt away," Guyroger Regoula told Reuters by telephone of sporadic clashes.
Shops were stripped of food and other provisions during the violence after the election result was announced on Thursday, Port Gentil resident Joel Adande said.
"What are they going to loot? They have looted everything already," he told Reuters by telephone.
Ben Bongo has appealed for an end to the unrest.
The capital Libreville has been relatively quiet but authorities were caught off guard in Port Gentil, where the French consulate and a sports and social club owned by French oil giant Total (TOTF.PA) were torched.
The city remained under curfew on Sunday. French paratroopers were guarding the consulate and Total has evacuated its expatriate staff and families to Libreville.
France maintained strong ties with Omar Bongo and is perceived by some Gabonese opposition supporters to have helped his son rig the election, something both Ben Bongo and Paris have denied.
"We are a country based on the rule of law and there are institutions which are there (to appeal the result)," Ben Bongo told French radio RFI.
"It is imperative that calm returns across the territory."
Leading opposition figures have said they will mount a legal challenge to the victory of Ben Bongo, who won 41.7 percent of the vote, according to the official tally. His two closest rivals won just over 25 percent each.
Omar Bongo ruled the Central African oil exporter for 41 years until his death in June. (Reporting by Linel Kwatsi; writing by Mark John; editing by Janet Lawrence)