DR Congo troops have fired three shells over the border into neighbouring Rwanda, injuring at least one person, during resurgent clashes with M23 rebel fighters, Rwandan officials have claimed.
Rwanda's UN ambassador Eugene Richard Gasana told the AFP news agency on Friday that his country would not hesitate to retaliate if the firing continued.
"If they are not ready to stop this, we will immediately act and it will hurt," he said, adding: “We will do it with laser precision, we know where it is coming from."
Rwanda is a current temporary member of the Security Council and Gasana said he had given his government's tough message to the other 14 members.
The council has asked for an investigation into the origin of Friday's shelling, diplomats said.
Fighting between the DR Congo army and M23 rebels resumed on Friday, both sides and the United Nations said just days after the latest effort at peace talks collapsed.
The violence continued throughout Friday, according to a statement from the UN Stabilisation Mission in the Democratic Republic of the Congo (MONUSCO), which went into action alongside Kinshasa's troops.
MONUSCO said it was "extremely concerned" about the resumption of hostilities, calling on the M23 rebels to return to the negotiating table.
"I am serious in our efforts to protect civilians and neutralise all armed groups to bring back peace and stability", said MONUSCO chief Martin Kobler.
Al Jazeera's Peter Greste, reporting from Nairobi, said while the fighting had calmed on Saturday morning, the situation remained tense in the region with thousands of people uprooted from their homes due to the renewed clashes.
Rwanda's ministry of refugee affairs said between 2,500 and 3,000 people had fled into the country via two border posts.
Both sides blamed each other for the fresh clashes.
M23 spokesperson, Vianney Kazarama, said the army attacked rebel positions early on Friday, but the military insisted it came under attack first - a claim supported by a source from the UN peacekeeping mission in the country.
On Monday, both sides announced a halt to peace talks taking place in the Ugandan capital, Kampala, despite UN pressure to end the year-and-a-half-old rebellion ravaging DR Congo's mineral-rich but volatile east.
According to the Congolese government, the talks were suspended due to disagreement over the extent of an amnesty for the army mutineers and their reintegration into the national army.
Backed by the international community, DR Congo's government is refusing to give amnesty to about 80 leaders of the M23 rebels and to enlist these men into military ranks.
Members of the M23 group are mainly Tutsi fighters from an earlier rebellion who were incorporated into the army in 2009 and then mutinied in 2012.
They took control of the provincial capital, Goma, for more than a week late last year before withdrawing under international pressure.
Kinshasa has long accused Rwanda of pulling the strings behind the rebellion and UN experts have even said that the M23's "de facto chain of command" was topped by Rwanda's defence minister.
Kigali has vehemently denied accusations that it is arming, financing the rebels - and even supporting them with its own forces.