The United States said on Sunday it was alarmed by an escalation in fighting in eastern Democratic Republic of Congo between M23 rebels and Congolese soldiers, and again called on neighboring Rwanda to stop its support for the rebels.
The State Department condemned attacks by the M23 that killed at least three people in Congo's eastern city of Goma on Saturday. It also expressed concern over reports by the United Nations of shelling by the M23 into Rwanda territory.
"We urgently call on (the) DRC and Rwandan governments to exercise restraint to prevent military escalation of the conflict or any action that puts civilians at risk," State Department spokeswoman Marie Harf said in a statement.
"We are deeply concerned about evidence of increasing ethnic tensions in Goma and call on all parties to avoid any actions that could exacerbate such tensions."
Harf said the United States was ready to consider further targeted sanctions against M23 rebel leaders and other armed groups.
Washington urged the U.N. mission in Congo, MONUSCO, to thoroughly investigate charges of cross-border shelling. Rwanda said five mortar bombs had fallen on Rwandan villages on Friday, following a rocket the previous day, and blamed Congo's army.
A 3,000-member U.N. Intervention Brigade has been deployed to fight and disarm rebels in the east.
Rwanda twice invaded its larger neighbor in the 1990s and sponsored rebels trying to topple the Kinshasa government. Millions have died since then in Congo's eastern border area, a patchwork of rebel and militia fiefdoms in an area rich in tin as well as tungsten and coltan ores.
A U.N. report in June said the M23 recruited fighters in Rwanda with the aid of sympathetic Rwandan army officers, while elements of the Congolese army have cooperated with the Rwandan Hutu rebel group FDLR.