GOMA, DRC — Congo severed diplomatic ties with Rwanda as fighting between Rwanda-backed rebels and government forces raged around the key eastern city of Goma, leaving at least 13 peacekeepers and foreign soldiers dead and displacing thousands of civilians. The M23 rebel group has made significant territorial gains along the border with Rwanda in recent weeks, closing in on Goma, the provincial capital of around 2 million people and a regional hub for security and humanitarian efforts. Congo, the United States and U.N. experts accuse Rwanda of backing M23, which is mainly made up of ethnic Tutsis who broke away