* PM protests at party's choice of former president's son
* Former interior minister also says he will run
(Adds appointment of new prime minister, paragraph 12)
By Linel Kwatsi
LIBREVILLE, July 17 (Reuters) - Gabonese Prime Minister Jean Eyeghe Ndong said on Friday he had resigned in protest at his party's choice of the son of deceased president Omar Bongo as presidential candidate and would stand against him in the poll.
The ruling Gabonese Democratic Party (PDG) on Wednesday named Defence Minister Ali Ben Bongo as its official candidate in the presidential election in the oil-producing West African country. The vote must be held before Sept. 6.
Ndong, who will run as an independent, said his argument was not with Bongo standing, but with the manner in which he was selected by the PDG.
"I am offering my candidacy outside the PDG simply because procedure was not respected," he told a news conference.
"From my position as prime minister, I have witnessed since the death of President Omar Bongo that senior figures in the PDG have begun a course of dividing the party and destabilising the state," he said.
Ali Ben Bongo was chosen by consensus, PDG deputy general secretary Angel Ondo said on Wednesday.
Opposition figures have expressed concern the election will be neither free nor fair, and will guarantee the succession of Ali Ben Bongo to the position his father held for more than four decades, during which he became one of Africa's richest men.
Separately on Friday, former interior minister Andre Mba Obame told France 24 television he would stand in the poll.
Obame said the result was not a foregone conclusion, and said the elections would take place on Aug. 30.
"I am a candidate because I think I have a political offer to make to the people of Gabon," he said.
An interim government took power on June 10, days after Bongo, Africa's longest-serving leader, died aged 73.
Rose Francine Rogombe, head of the interim government, appointed Paul Biyoghe Mba, formely minister of agriculture, as prime minister later on Friday.
The former French colony's constitutional court last week approved an extension to the 45-day period for which the interim government is constitutionally allowed to rule.
French energy company Total is one of the biggest investors in Gabon, which produces about 273,000 barrels of oil per day. (Additional reporting by Tamora Vidaillet in Paris; writing by Daniel Magnowski; editing by Tim Pearce)