* EU says result for Bongo stronghold anomalous
* AU to send delegation, likely led by Chad President
* France suggests recount, says nationals missing
* Calm prevails in capital, Libreville (Adds government spokesman, background)
By Gerauds Wilfried Obangome
LIBREVILLE, Sept 6 (Reuters) - Gabon's re-elected president, Ali Bongo, came under international scrutiny on Tuesday as a European Union mission questioned the validity of his narrow win, France recommended a recount and the African Union said it would send mediators.
At least six people died in riots in Libreville and other cities in the days after the announcement of results from the Aug. 27 election, which gave Bongo the victory by about 5,000 votes. Calm has since returned to the streets, witnesses said.
Election monitors have focused on the southeastern Haut-Ogooue province, a Bongo stronghold where official figures showed he won 95.46 percent of the vote on a 99.9 percent turnout.
Opposition leader Jean Ping says the election was stolen, with the number of votes cast in Haut-Ogooue inflated to give victory to Bongo, whose family has ruled the central African oil-producing country for almost half a century.
The EU observer mission said the number of non-voters and blank or invalid ballots were at variance with the reported participation rate, adding turnout in other regions was around 48 percent.
"The integrity of the provisional results for this province is consequently put into question," said Mariya Gabriel, the EU's chief observer of the polls.
A government spokesman told Reuters he would not comment on the EU statement until Wednesday.
Opposition parties in Africa frequently say votes are rigged, but the results are rarely overturned and it is unusual for a president once declared winner to face significant international pressure over the election.
The African Union said it would send a delegation to Gabon likely to be led by Chad's Idriss Deby, one of Africa's longest-ruling presidents and the current chair of the pan-African body. expect the high-level delegation to be dispatched very soon," African Union spokesman Jacob Enoh Eben said.
Manuel Valls, prime minister of former colonial power France, suggested a recount would be wise and urged authorities to help locate about 15 of its nationals - out of a local French community of around 14,000 - it says are missing.
Gabon's opposition has yet to say if it will appeal through the Constitutional Court for a recount, while the government has dismissed all calls to publish more detailed results, prompting the justice minister to resign.
Ping, a former diplomat and African Union Commission chairman, said he welcomed all efforts at mediation, adding: "We want democracy and peace to triumph."
Calling for calm, he told French broadcaster France24 that 50 to 100 people had been killed since last week, figures that could not be independently verified.
ORDER RESTORED
A main opposition complaint is that Gabon's oil wealth has not been shared fairly among its 1.8 million population. But largely ignoring an earlier strike call by Ping, shopkeepers and government staff returned to work in the capital, Libreville, on Tuesday.
Parliament also resumed, with lawmakers gathering sombrely in the Senate building after part of the National Assembly complex was badly damaged during last week's protests.
France has in the past intervened in its former African colonies, such as when it helped oust Cote d'Ivoire's then-president, Laurent Gbagbo, in 2011 after he refused to concede defeat in an election.
But it has ruled out intervention in Gabon where it has a military base.
Up to 1,100 people were arrested last week during the unrest, according to the interior minister, although many have since been released.
U.N. human rights spokeswoman Ravina Shamdasani said on Tuesday the organisation was following the situation in Gabon with "increased concern".