CECILE MANTOVANI NEARLY  half of all the violence visited on African migrants during their journey to the Mediterranean coast is perpetrated by law enforcers, the United Nations refugee agency UNHCR has said. According to a report by UNHCR and the Danish Refugee Council's Mixed Migration Centre (MMC), thousands of refugees and migrants suffer extreme abuse including torture and sexual or gender-based violence, and in some cases death. The report is based on nearly 16,000 interviews with refugees and migrants. "In 47% of the cases, the victims reported the perpetrators of violence are law enforcement authorities, whereas in the past, we…