The US on Wednesday urged Russia to rein in a mercenary force that is fighting in a civil war in the Central African Republic, pointing to evidence of lootings, mass killings and other abuses. Linda Thomas-Greenfield, Washington’s UN envoy, said Russian mercenaries were operating on behalf of defence chiefs in Moscow in the landlocked African nation and have been linked to “horrific acts” there. Her comments follow a report by UN monitors on the arms embargo imposed on Bangui in 2013 which found that Russian military trainers and Central African Republic forces had indiscriminately killed civilians, occupied schools and looted towns. “The UN has provided evidence, including eyewitness accounts, detailing violence and abuses carried out in the Central African Republic by mercenaries working as an arm of Russia’s Ministry of Defence,” Ms Thomas-Greenfield said. “Russia must immediately stop the violence, hold those responsible accountable and remove mercenaries endangering UN peacekeepers." Russia has sent hundreds of military experts to arm and train government troops fighting rebels in the resource-rich ex-French colony, which collapsed into civil war in 2013. The paramilitary troops from the Russian group Wagner are reportedly well connected in the Kremlin and even reputedly have ties to President Vladimir Putin — though Moscow denies any involvement with the group. Russia’s UN envoy Vassily Nebenzia on Wednesday rejected the findings of the UN panel. "We saw this report, analysed it and prepared comments to it, which were fully ignored,” Mr Nebenzia told reporters in New York. “This is the same story: unfounded accusations, evidence collected God-knows-where, witnesses who cannot be identified.” Government officials from the Central African Republic have also rejected the report. The country has been wracked by violence since the Seleka coalition of mostly Muslim rebels seized power in March 2013. The Central African Republic's military, backed by UN peacekeepers as well as Russian and Rwandan troops, has in recent months been battling the rebels. US President Joe Biden and his counterpart Mr Putin tackled worsening US-Russia ties at a summit in Geneva earlier this month, but they continue to disagree over everything from cyber attacks to the wars in Syria, Ukraine and the Central African Republic.