Gabon opposition leaders say one person has been killed and more than 20 injured after the presidential guard attacked the party's headquarters overnight following protests against the re-election of the president.

Authorities said President Ali Bongo Ondimba defeated opposition candidate Jean Ping by a slim margin.

Paul Marie Gondjout, an opposition electoral representative, said Thursday that soldiers in green berets shot live rounds during an attack on the headquarters, injuring at least 20.

Rene Ndemezo'o Obiang, Ping's campaign director, said one person was killed. Ping was not in the building.

Demonstrators had set fire to cars and buildings, vandalized a mall and looted a bank in the capital.

Authorities said Bongo won Saturday's election with 49.8 percent of the vote, while Ping had 48.23 percent.