Twenty-seven people were killed in South Sudan's Central Equatoria State in tit-for-tat violence between cattle herders and members of a militia Thursday, a day before Pope Francis' scheduled visit, a county commissioner told Reuters.  After fighters from a rebel group killed six people from a herding community, herders retaliated by killing 21 civilians in a nearby area. The victims include five children and a pregnant woman, Kajo-Keji county commissioner Phanuel Dumo said.  The pope arrived in Juba from neighboring Kinshasa Friday and is hoping to jolt a peace process aimed at ending a decade of conflict fought mostly on ethnic lines that has killed hundreds of thousands of people.