By David Lewis and Sonia Rolley NAIROBI - As Rwanda-backed M23 rebels in eastern Democratic Republic of Congo push south towards the city of Bukavu, they are likely to have to fight their way through thousands of troops from Burundi,

Rwanda-backed rebels were quickly expanding their presence in eastern Congo after capturing Goma, the region's major city, the U.N. said Friday, also expressing concerns over executions it learned were carried out by the rebels following a major escalation of their yearslong rebellion.

Much of the beleagured city of Goma was calm early Wednesday morning, after a day during which thousands of fleeing people hunkered down by roadsides as missiles flew and injured people streamed to overwhelmed hospitals.