Fighting has escalated sharply in recent weeks in eastern Congo, where rebels have seized key towns and are closing in on the city of Goma, the government’s last stronghold in the region bordering Rwanda. The offensive by the Rwanda-backed M23 rebel group has stretched local hospitals to the limit, with hundreds of wounded coming in every day as civilians get caught in the crossfire. Explosions from Goma's outskirts have been reverberating across the city of 2 million people this week.