The government, with the support of a 12,000-strong U.N. peacekeeping mission, has been trying to calm the country that descended into sectarian fighting in 2013 when Muslim rebels overthrew the Christian president. [...] large parts of one of the world's poorest countries remain unstable, and the U.N. mission has said it doesn't have enough troops to protect civilians. In Bria, more than 20 people were killed in the recent fighting between armed groups, likely elements of a mostly Muslim Seleka faction clashing with elements of Christian anti-Balaka rebels. The U.N.