The UN rights chief on Friday called on Sudanese authorities to launch an independent investigation after security forces killed at least nine demonstrators attending a mass protest demanding an end to military rule. Michelle Bachelet said in a statement that she was “alarmed” at Thursday’s killings, including of a 15-year-old child, “even after the police had announced they would not use lethal force to disperse the demonstrators”. The mass demonstration, which saw tens of thousands turn out across the country, was met with the deadliest violence so far this year. The death toll from protest-…