FISTON MAHAMBA  AT least two students and a teacher were killed and several other teachers kidnapped after a primary school holding exams was attacked by unidentified gunmen in eastern Congo, authorities and the United Nations have said. Exact details of the attack and the number of casualties remained unclear. Congo's President Felix Tshisekedi said two students died when fighting broke out in North Kivu province on Thursday morning. He did not give further details. Cosmas Kangakolo, an administrator for Masisi territory, said the Ngoyi Primary School was attacked. He said one teacher died and several were kidnapped. Exam centres in…