By Joe Bavier

GAMINA, Ivory Coast May 7 (Reuters) - Nestled among the cocoa plantations of western Ivory Coast is a gold mine that does not feature on any official maps. It is not run by an industrial mining company, nor does it pay taxes to the central government.

The unlicensed mine is a key part of a lucrative business empire headed by the deputy commander of the West African nation's elite Republican Guard, United Nations investigators allege. He is one of the principal players in a network of senior officers - former rebel commanders who have integrated into the Ivorian army - that has seized control of mines that generate tens of millions of dollars a year, and that engages in illegal taxation, smuggling and racketeering, they say.

Interviews with more than two dozen military insiders, diplomats, U.N. officials, local authorities, analysts and miners also reveal that the network of former rebels continues to maintain loyalist fighters under their exclusive control. A confidential U.N. arms inventory, reviewed by Reuters, showed that one former rebel commander possesses enough weapons - from surface-to-air missiles to millions of rounds of ammunition - to outgun the Ivorian army.

A senior Ivorian army officer said that the network represents a parallel force within the military that threatens the stability of the country, which has emerged from a 2011 civil war as one of Africa's fastest growing economies.

Elections in October are expected to return President Alassane Ouattara for a second and final term. But some former rebel commanders are loyal to rival political figures. As politicians position themselves to follow Ouattara, they risk dragging the country back into turmoil.

"I don't know how we're going to sort this out," said the senior army officer. "They (the former rebel commanders) are completely out of our control."

"THE ONLY WORK THERE IS"

A hundred metres or so beyond a checkpoint manned by armed former rebel fighters outside the village of Gamina, a deep trench runs through what used to be rice fields. Thousands of men hack through the earth and rock with picks and chisels as a handful of soldiers look on from above.

Two years ago a rubber farmer here struck a vein of gold ore. Today, a sprawling system of pits, trenches and underground tunnels covers some 180 hectares (445 acres). The mine employs nearly 16,000 workers and produces gold worth nearly $97 million a year, according to U.N. investigators.

Labourers have flooded in and say that, with luck, they can make up to 250,000 CFA francs ($430) in a few weeks, about what they would earn in a season working on a cocoa plantation.

"This is the only work there is," beamed Adama Bamba, a 26-year-old mud-caked miner. "It's a dog's life under the cocoa trees."

The mining is backbreaking and dangerous. Miners and local villagers told Reuters that dozens of bodies, victims of regular cave-ins, are buried in unmarked graves beneath nearby coffee trees. Others have been left in the rubble at the bottom of the pits, some of which cut down 60 metres into the earth.

A U.N. expert panel charged with monitoring an arms embargo imposed on Ivory Coast by the Security Council, as well as military sources at the mine and within the Ivorian army, say the Gamina mine is controlled by Lieutenant-Colonel Issiaka Ouattara (no relation to President Ouattara). Issiaka Ouattara is a former rebel leader who is now the deputy commander of the Republican Guard and a man known ubiquitously by his three-syllable nom de guerre: Wattao.

A Reuters reporter witnessed soldiers loyal to Wattao in control of the mine and overseeing the miners. Those soldiers were also present inside the "comptoirs," or offices where the miners sell the gold they find.

One of the soldiers based at the mine told Reuters that he was an ex-rebel who had gone through a donor-backed disarmament programme but returned to his old unit. He said other soldiers in Gamina had done the same or were still waiting to go through the programme. He named his two commanders and said those officers answered to Wattao. A senior army officer familiar with the operation confirmed to Reuters that Wattao controlled local fighters and the mine.

Wattao denies any involvement in the mining operation or the existence of a private force of loyalist fighters. "These are pure lies ... I've never been involved in gold," he told Reuters by telephone in April. "They're looking to find some false problem at all costs in order to put Wattao under sanctions."

"COM'ZONES"

A corporal in the army in 1999, the first year of Ivory Coast's 12-year-long political crisis, Wattao rose to become one of the most powerful commanders in the New Forces, a rebel movement headed by a former student leader named Guillaume Soro.

During the New Forces' nine-year occupation of the north, which effectively split the country in two, the rebels divided their territory into multiple zones. Each was headed by a commander known as a com'zone. The com'zones - Wattao was one - were responsible for security and collecting revenues that were funnelled to a treasury known as "La Centrale."

La Centrale was dissolved after the end of the civil war in 2011 and the commanders integrated into the army.

But according to a 2013 report by the U.N. investigators, some of the former com'zones took advantage of their integration to extend "their warlord-style predatory economic activities," including the control of gold and diamond mines, smuggling cocoa, cotton and cashews, and levying illegal taxes on trade and transport.

The U.N. monitors estimate that miners at Gamina dig up as much as 11.5 kg (25 lb) of gold a day. That "would account for 13.8 percent of the country's annual official (gold) production," the monitors wrote in their latest report published last month. Using a conservative gold price of $1,210 per ounce, they estimated the value of Gamina's annual output at $96.8 million.

Ivory Coast officially produces less than half as much gold as neighbouring Mali and about a fifth as much as Ghana. But the government is keen to boost the mining industry.

"PIECE OF THE CAKE"

Small-scale artisanal miners told Reuters the local "comptoirs" pay 14,000 CFA francs per gram - or just $740 per ounce - around 60 percent of the current gold price. Ex-rebels and security guards employed by the buyers search miners to ensure they do not sneak ore off-site, one soldier at the mine said.

The main buyers all sell their gold exclusively to Wattao and three partners, the U.N. investigators allege. Two other sources, who have either worked in the mine or are familiar with its operations, confirmed the system to Reuters. The partners are "highly visible political figures involved in the current Ivorian administration and the past administration of Burkina Faso," the U.N. report said, declining to give their names due to mandate restrictions.

Early last year, a buyer not affiliated with Wattao or his partners sought to set up a rival office to buy gold at a higher price. He was killed soon after, according to the investigators.

Wattao denied any involvement. "I've never had elements over there," he told Reuters.

Mines Minister Jean-Claude Brou declined Reuters' requests for comment, but he has previously said that no artisanal mining permits are currently valid in Ivory Coast. A senior ministry official confirmed this and the head of one of the "comptoirs" told Reuters that he and other buyers had applied for, but not received, semi-industrial mining permits to work the Gamina mine.

A villager who until recently collected taxes for the local council from the myriad businesses that have grown up around the mine said: "The (local and regional) authorities know what's going on, but they keep quiet, because every two weeks they get their piece of the cake."

Reuters reviewed copies of contracts between some of the buying offices and landowners and tenants. The contracts list fees paid to landowners, farmers, village authorities and the local and regional governments for every gram of gold mined. One buying office also agreed to build an office and new residence for the local sub-prefect, according to documents and village authorities.

The sub-prefect, Marcel Goue, denied any wrongdoing and said the involvement of local authorities had improved the situation. "We're fighting to clean up the site," he said.

The U.N. investigators estimate that in addition to Wattao's gold earnings, he makes more than $1.7 million a year charging the agents in the "comptoirs" fees for the security he provides around the mine. Based on annual production and the security fee per gram printed in the contracts, that's enough to pay the salaries of some 500 fighters, the investigators estimate.

SECRET ARSENAL

Wattao once gave a French television reporter a ride in his Maserati before showing him around his luxury beach compound. But he is not the only former rebel under the spotlight.

Defence Minister Paul Koffi Koffi said he was not aware of any ex-com'zones being involved in illegal activities. The government had given them top army jobs to make them answerable to the military hierarchy, he told Reuters in an interview. "The solution was to make them leaders. They were named commanders of units or deputy commanders of units with their men integrated into the ranks."

But critics claim the promotions have emboldened the former rebel commanders and made them virtually untouchable. U.N. efforts to trace their weapons since the civil war have been repeatedly stymied.

On March 25, according to a confidential letter to the U.N. Security Council's Ivory Coast sanctions committee seen by Reuters, inspectors finally got full access to the camp of an ex-com'zone named Martin Fofie Kouakou. Kouakou was promoted to the rank of lieutenant-colonel in the army earlier this year despite appearing on a U.N. sanctions list for alleged human rights abuses.

What the inspectors found was a 60-tonne arsenal. According to the letter, Alain-Richard Donwahi, secretary of President Ouattara's National Security Council, acknowledged that most of the weapons stockpiled at the camp were not under state control.

An inventory of the arms cache reviewed by Reuters listed hundreds of heavy machine-guns and assault rifles, dozens of multiple rocket-launchers, mortars, rocket-propelled grenade launchers, and even SAM7 surface-to-air missiles. The inspectors also found 2.8 million rounds of small arms ammunition, 113,000 heavy machine-gun rounds, 4,680 rounds of grenade launcher ammunition, 1,200 anti-tank rockets, and more than 2,000 other assorted bombs, rockets and artillery shells.

"Heavy weapons observed outmatching the firepower of the entire FRCI (Ivory Coast's armed forces)," wrote Raymond Debelle, coordinator of the Ivory Coast group of experts.

Debelle would not comment publicly on the letter. Kouakou did not answer repeated calls requesting comment.

Much of the hardware in the cache was manufactured between January and August 2011 and was still in packing crates, according to the letter, indicating that at least some of it was acquired after the civil war, which ended in April of that year, and after the rebels had merged into the army.

"None of this stuff was under government control," one Abidjan-based Western diplomat familiar with the U.N. inspection said. "You've got people within the security forces maintaining a secret stockpile of weapons. That's a problem."

The U.N. arms embargo on Ivory Coast began in 2004. Though the ban was loosened last year to allow selected arms imports, none of Kouakou's weapons were declared to the U.N., a likely violation of the embargo.

When contacted by Reuters, Donwahi would not comment on whether the arms stocks constituted an embargo violation, saying the U.N. experts were continuing their investigations.

"The President of the Republic has given firm instructions to the Army Chief of Staff to place these weapons and ammunition under guard," he said. "A country that is emerging from a crisis has, indeed, many weapons in circulation, and bit by bit we will put things in order." (Additional reporting by Ange Aboa and Loucoumane Coulibaly in Abidjan; Edited by Simon Robinson)