Rwanda had late on Monday accused government troops of deliberately bombing its territory.
The M23 rebels are former soldiers who mutinied in April after the failure of a 2009 peace deal that integrated them into the regular army.
The fighting is the most serious since July, when UN helicopters last went into action against the M23.
The mineral-rich east has long been a powderkeg, the launchpad of rebellions dating back to 1996, with Rwanda and Uganda both playing active or behind-the-scenes roles in much of the warfare.
Two wars that shook the whole of DR Congo between 1996 and 1997 and then again from 1998 to 2002 both began in the Kivu region.
Since 1998 more than three million people are estimated to have died from combat, disease and hunger and 1.6 million have been left homeless.
The former Belgian colony, known as Zaire under the dictator Mobutu Sese Seko who was toppled in 1997, remains one of the world’s least developed countries despite a wealth of cobalt, copper, diamonds and gold.
In peaceful times, Goma is the starting point for tourists wishing to see endangered mountain gorillas in nearby Virunga National Park.
About The Author
