ABIDJAN (Reuters) - Three demobilized ex-rebel fighters were killed in Ivory Coast’s second-biggest city of Bouake on Tuesday, as they clashed with police attempting to end their protest over bonus payments, a policeman and a spokesman for the former fighters said.

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The police source said another 20 wounded, which he believed to be mostly former rebels, were being treated at the city’s main hospital.

French-speaking West Africa’s most important economy has rapidly recovered from a decade-long crisis ending in a 2011 civil war, but unrest among mutinous soldiers and former rebels has exposed just how fragile those gains are.

Bouake was at the epicenter of two major army mutinies this year that revealed President Alassane Ouattara’s tenuous grasp on his military and associated armed groups.

The unrest also affected ports that ship cocoa out of the world’s leading producer, causing prices to briefly spike.

Tuesday’s violence erupted after former members of a northern rebellion who helped Ouattara to power in 2011 -- and are demanding 18 million CFA francs ($30,800) as a reward -- blocked the main southern entrance into Bouake.

Amadou Ouattara, a spokesman for the ex-rebels, said policemen had fired teargas before shooting into the crowd.

“It was three demobilized fighters who were killed. They were unarmed,” he said. “The police started shooting tear gas ... At the same time they started shooting (live bullets).”

A policeman on the scene in Bouake disputed that version. The officer, who asked not to be named as he was not authorized to speak, said one of the demobilized combatants had a grenade which exploded accidentally, killing three people at the scene and wounding more than 20.

Ouattara’s government last week agreed to pay around 8,400 mutinying soldiers 5 million CFA each, ceding to their demands in order to end a four-day uprising that blocked roads and shuttered businesses in most cities and towns.

However, the deal risks angering other factions in the military, which is still riven by civil war-era divisions between ex-rebels and former loyalist soldiers.

Tuesday’s protesters were part of a group of some 6,800 combatants demobilized following the conflict but who claim they are still owed money for their service. They first took to the streets earlier this month.