President Ali Bongo's ruling Gabonese Democratic Party (PDG) has won a legislative election by a landslide in the first round, the presidency said.

"We have observed what looks like a landslide in favour of the (ruling) majority," presidential spokesperson Ike Ngouoni said on Sunday, citing results posted publicly at voting stations.

He said the PDG had won 80 of the 143 seats in the national parliament.

Ngouoni said turnout was "relatively weak."

The presidential spokesperson said the electoral authority would announce definitive results later Sunday or on Monday.

Some opposition candidates and witnesses who spoke to the AFP news agency at polling stations alleged voting irregularities.

They said voting papers had gone missing, there had been attempts to buy votes, and opposition representatives had been denied access.

People in the oil-rich West African country voted on Saturday in a long-delayed legislative and municipal vote, the first to be held since a presidential election two years ago was marred by deadly violence and fraud allegations.

President Bongo's key rival, Jean Ping, boycotted the election, but most opposition groups took part.

Gabon has been ruled by the same political dynasty for nearly half a century.