More than 400 people have been killed in recent attacks by the paramilitary Rapid Support Forces (RSF) in Sudan's Darfur region, the UN says, citing "credible sources". Last week, the RSF launched an intense ground and aerial assault on refugee camps surrounding the city of el-Fasher in an attempt to seize the last state capital in Darfur held by their rival, the Sudanese army. Sudan's civil war began exactly two years ago, causing what aid agencies call the world's worst humanitarian crisis