UN troops are ready to use "lethal force" to stop a rebel advance on the Democratic Republic of Congo city of Goma after major new clashes erupted, a spokesman said Monday.
The DR Congo government said at least 130 people, including 10 soldiers, were killed in new fighting with M23 rebels on the outskirts of Goma in the east of the country on Sunday.
The UN has deployed a 3,000 strong intervention brigade in eastern DR Congo in recent weeks. The joint South African, Tanzanian, Malawian brigade has an unprecedentedly strong UN Security Council mandate to take on armed groups.
The DR Congo "mission has put its troops on high alert and stands ready to take any necessary measures including the using of lethal force to protect civilians," UN spokesman Martin Nesirky said.
"Any attempt by the M23 to advance toward Goma will be considered a direct threat to civilians," he added.
M23, which UN experts say has received backing from Rwanda and Uganda, briefly took Goma in November last year, sparking the UN decision to beef up its forces in a region where millions have died in conflict over the past two decades.
The latest heavy fighting broke out at Mutaho, about eight kilometers (five miles) northwest of Goma, the UN mission in DR Congo, MONUSCO, said.
The M23, which has forces around Goma, has reinforced its positions with "heavy artillery" and a "battle tank," MONUSCO said in a statement.
The clashes erupted as the Rwandan government accused commanders of the the UN's Force Intervention Brigade (FIB) of meeting leaders of the rebel Democratic Forces for the Liberation of Rwanda (FDLR).
The FDLR is mainly based in eastern DR Congo and includes ethnic Hutu fighters accused of taking part in Rwanda's 1994 genocide.
"Rwanda has credible, reliable and detailed information that various forms of tactical and strategic collaboration with the FDLR were discussed during those meetings," Rwanda's UN ambassador Eugene-Richard Gasana said in the letter.
"Their actions, implicating senior United Nations commanders picking sides among the very armed groups whose military activities they are meant to deter, are of serious concern," he added.
Gasana also said there is "enhanced collaboration" between the DR Congo army, the FARDC, and the FDLR, "often with the knowledge and/or support of certain FIB contingents."
"There are increased patterns of large quantities of weapons and ammunition, being delivered to FDLR by FARDC officers," the letter said. It added that UN force commanders knew about the deliveries.
Gasana said the activities could "undermine" a regional peace accord brokered by UN leader Ban Ki-moon and signed this year by African leaders. Under the accord, the leaders promised not to interfere in each other's affairs.
The United Nations declined to comment immediately on the letter.
UN experts monitoring DR Congo sanctions said in their latest report that Rwanda was still aiding the M23 though the assistance has fallen off since last year.