GENEVA (Reuters) - United Nations human rights experts called on Uganda on Tuesday to rein in violent security forces and drop charges against political opponents and activists arrested in what the experts termed an election clampdown. Pop star Bobi Wine has emerged as the strongest challenger to President Yoweri Museveni in the presidential election scheduled for Jan. 14. On Sunday Wine, whose real name is Robert Kyagulanyi, said one of his bodyguards was killed when military police ran him over while Wine’s convoy was taking a wounded journalist to seek medical help. Military police said the bodyguard had fallen from a speeding car. “We are gravely concerned by the election-related violence, the excessive use of force by security personnel, as well as the increasing crackdown on peaceful protesters, political and civil society leaders and human rights defenders,” the U.N. experts said in a statement. Both the president’s and government’s spokesmen declined to take calls from Reuters seeking comment. Wine says violence by security forces against his presidential campaign has escalated as popular support for it has grown. In November, at least 54 people died after protests erupted following Wine’s brief detention over alleged violations of COVID-related social distancing measures. Police said at the time they arrested nearly 600 people and accused protesters - who authorities deployed the military to help disperse - of rioting and looting. Rights lawyer and government critic Nicholas Opiyo was charged with money laundering last week in a case his organisation said was part of a crackdown on dissent and which the U.N. experts said appeared to be “strictly related to the electoral context”. Opiyo heads watchdog Chapter Four Uganda, which has helped to defend leaders and supporters of opposition parties detained on political charges. In the past five months, there have also been 16 attacks on journalists covering election-related events, according to the Human Rights Network for Journalists-Uganda.