Rwanda-backed rebels who captured eastern Congo's largest city said Thursday they want to take their fight to the far-off capital, Kinshasa, while Congo’s president called for a massive military mobilization to resist the rebellion and his defense minister rejected calls for talks.

The United Nations expressed deep concern at reports of M23 rebels and Rwandan troops advancing south towards the Congolese city of Bukavu on Thursday, as the militants sought also to assert their control over east Congo's largest city Goma.

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.