It has on several occasions clashed with the FDLR, who are accused of orchestrating the 1994 Rwandan genocide in which up to a million minority Tutsis were slaughtered by the majority Hutus.
The FDLR fled to the DRC when the current Rwandan government seized power after waging an armed rebellion.
Although the DRC's 1998-2003 war has officially ended, the central African nation's eastern provinces remain plagued by lingering fighting between the army, rebels and local militias.
Monuc backs the army's operations against the FDLR, seen as a root cause of the violence in eastern Congo.
Doss said he agreed with the assessment by the International Committee of the Red Cross (ICRC) that the humanitarian situation in the east of the country was still dire.
"In those areas where the FDLR has been entrenched - and entrenched for many years I might add - the situation has got worse," he said.
"I [do] recognise that - and that's why we must do everything we can to minimise the impact and move ahead with these operations, and try finally to put an end to the FDLR menace, which has disrupted and created great instability in North Kivu for many, many years."
Doss said that in a number of cases, the FDLR had attacked civilians without being attacked by UN forces.
"The FDLR is a very violent and brutal group, as we know. They haven't always waited for an operation to start," he said.
"They have held sway in these areas for a long time; they control important economic assets and they are not anxious to lose them.
"They will use violence when they think they need to. Our help has been much more than military operations."
Doss said Monuc had deployed military bases all over - in North and South Kivu - and set up temporary bases "sometimes to be closer to the population".
"We have joint protection teams out there seeing what's going on; helping not just to react to violence but to prevent violence," he said.
Earlier, Doss had told the UN Security Council that a spate of reprisal attacks by fighters of the Ugandan Lord's Resistance Army (LRA) and the FDLR had caused "new civilian displacements and serious human rights violations".
The Congolese army has been blamed for some of these violations.
Meanwhile, the arrival of 3,000 extra peacekeepers in the DRC, aimed at supporting the UN mission there, has been delayed.
"So far, I have to be frank, none of those troops are in the country. I hope that they will be in the next two to three months," Doss said.
"We have reasonable assurances now that the first elements will start to arrive in the next couple of months."