Renewed fighting has broken out around Goma, the capital of North Kivu province, close to the Democratic Republic of Congo's border with Rwanda.
And UN peacekeepers are taking a more combative role as fighting escalates in the DR Congo.
Its elite intervention brigade, which has been given a robust mandate to take on armed groups, has been drawn into the fight, changing the dynamic of the conflict in DRC's troubled east and raising questions about the UN's aggressive new military mandate.
We have a very complex situation where people want to drag the United Nations into a military solution, and a military confrontation which would expand; and there is a real risk of [a] regional war if this military options prevail.
M23 rebel fighters briefly seized the city in November, but withdrew in return for a promise of peace talks, however, those talks in Uganda have made little headway.
And they are now being accused of rocket and mortar attacks on Goma, and shelling neighbouring Rwanda. The group blames the cross-border attacks on the Congolese army.
M23 is the largest rebel group in DR Congo. It takes its name from an agreement on March 23, 2009 which integrated fighters into the DRC's national army. But in April last year, many deserted the group, complaining of discrimination and poor treatment.
However, there are an estimated 2,000 fighters in the movement. In November, they dealt a serious blow to the credibility of what is the world's largest peacekeeping force, marching past UN soldiers to seize Goma.
That seems unlikely to happen again as the new UN Intervention Brigade, set up last month, is authorised to carry out what are described as 'targeted offensive operations', meaning they can fire first.
UN peacekeepers gave M23 rebels 48 hours to lay down their arms at the beginning of August but that deadline was ignored.
Tensions are now being strained further, after UN peacekeepers from Uruguay were accused of shooting dead two people during protests over the latest fighting.
It is all serving to raise the stakes for the UN peacekeeping mission, and raising concerns that its new, more offensive mandate could backfire.
So, are there contradictions within the new UN role inside DR Congo? Will the UN escalate operations in the country and what will it mean for the pursuit of peace in DRC?
To discuss this, Inside Story with presenter Shihab Rattansi, is joined by guests: Felix Basse, spokesman for United Nations Organization Stabilization Mission in the Democratic Republic of the Congo (MONUSCO); Kambale Musavuli, spokesman for Friends of the Congo, a group pressing for peaceful and lasting change in DRC; and Marc-Andre Lagrange, senior analyst for Central Africa at the International Crisis Group.
"... The real tragedy here is that we have a population that's been indiscriminately bombed … the Congolese lives have no value … we can discuss about M23 and the complexity of the militia groups there [but] what is clear is that we know who supports the M23, we know that is supported by Congo's neighbour Rwanda, and there are things that need to be done, and that are not being done right now … Rwanda is not being held accountable for the situation …"
- Kambale Musavuli, spokesman for Friends of the Congo