* Mines, corruption and food prices focus of Bio's criticism
* Election to test Sierra Leone stability, progress
By Simon Akam
FREETOWN, Oct 9 (Reuters) - Sierra Leone's main oppositioncandidate in a November election has kicked off his bid for thepresidency with an attack on the incumbent's record on mineralsdeals, corruption and rising food prices.
The comments from Maada Bio, a former junta leader seen asErnest Bai Koroma's biggest threat for re-election in the Nov.17 vote, on Tuesday divided the local press and were rejected bythe president's camp as political manoeuvring.
Koroma is seen as favourite but Bio has strong support,especially amongst youth and will likely force a run-off vote.
The election will be a crucial bellwether of the country'sprogress a decade since its civil war ended.
"Under Obai, our mineral wealth has been more mortgaged andwith lesser returns to the citizenry than before he tookoffice," Bio said, referring to Koroma by a form of his middlename, in a speech broadcast on a local radio station on Mondaynight.
Sierra Leone is rich in natural resources, including ironore, bauxite, diamonds and rutile but was at war for most of the1990s and is struggling to rebuild. It has found oil though itis unclear yet whether there are commercially viable quantities.
In an interview with Reuters last year Bio said if electedhe would review minerals deals, some of which have beencriticised for failing to conform to Sierra Leone's own laws.
He did not provide any further details during interviewswith several radio stations but did attack Koroma's record ongraft.
"The abuse of public office for private gain is growing intoan art and impunity has reached intolerable levels, higher thanbefore he took office," Bio said.
When he came to power in 2007 Koroma promised there would be"no sacred cows" in his administration. However, last week heretained his vice president as running mate despite Samuel SamSumana's involvement in a series of scandals.
SECURITY A CONCERN
Politics in the country of six million is largely drawnalong ethnic lines.
The ruling All People's Congress draws its support from theTemne and Limba peoples of the north. Bio's Sierra LeonePeople's Party has its base in the Mende of the south and east.
"On Nomination Day... Bio Fires Warning Shot," The New Stormsplashed on its front page. "Maada Bio's days are numbered," TheTorchlight newspaper, which described the challenger'snomination as lacklustre, hit back.
A United Nations peacekeeping force left the country in2005. While the country has remained largely peaceful since thewar, it has seen pockets of rioting over the last year.
Last week, Richard Howitt, the head of the European Union'selection observer mission, said security around the election wasthe team's biggest concern.
Bio blamed Koroma for a spike in food prices, saying theyhave risen three-fold since he took office. Prices have risen inthe West Africa state, though Nasri Halloway, a rice importer,said it was closer to doubling than tripling.
Unisa Sesay, Koroma's spokesman, dismissed Bio's criticism."All the points he's making are only in the nature ofpoliticking," he said.
Sesay said Sierra Leone's anti-graft commission was free ofpolitical interference. He accepted that some mistakes had beenmade during negotiations but said all mining contracts had beenratified by parliament.
"We are all human beings ... We are not perfect, we don'thave all the information," he said, adding that a process ofreviewing deals was already under way.
(Writing by David Lewis and Richard Valdmanis)
Keywords: SIERRALEONE ELECTION/