The UN has warned of a growing humanitarian crisis in the Democratic Republic of Congo, after rebels took the eastern city of Goma on Tuesday.
Aid officials said the fighting has made camps for people displaced by earlier conflicts inaccessible, with food and medicines running short.
Armed groups have battled over eastern DR Congo for two decades. The M23 rebel group was formed eight months ago by soldiers who defected from the army, the BBC reports.
M23 is widely believed to be backed by Rwanda and Uganda. The rebels have now advanced beyond Goma, the biggest city in eastern DR Congo, taking the town of Sake.
They have threatened to march on the capital, Kinshasa, if President Joseph Kabila does not open negotiations with them.
About 500,000 people have been displaced by the rebellion since April and there are fears of renewed war in DR Congo.
Some five million people died in a civil war lasting from 1997 until 2003.