On Monday a UN military spokesman said about 600 UN peacekeepers and 3500 Congolese government troops were still fighting Ugandan rebels south of Beni in Democratic Republic of Congo's North Kivu district.
Over the last week, joint Congolese-UN units had also staged two operations to flush out local Congolese militias which carried out attacks and refused to lay down their arms in Ituri district, which lies to the north of North Kivu.
Major Hans-Jakob Reichen, the UN military spokesman, said: "Some 80 armed members of these ex-militia and rebel groups, both Congolese and Ugandan, have been killed in the last week."
The three operations were mounted after a ground-breaking national referendum on 18 December in which Congolese overwhelmingly voted to adopt a new constitution aimed at paving the way for national elections by the end of June.
The internal security drive is key to guaranteeing peaceful parliamentary and presidential polls in Africa's third-biggest country, which has suffered decades of dictatorship, war and chaos.
Reichen said: "This is a momentum we will sustain right up to the elections."
He said UN casualties reported in the week's operations so far were an Indian peacekeeper killed and four more wounded.
"This is a momentum we will sustain right up to the elections"
Major Hans-Jakob Reichen,
UN military spokesman
Some Congolese government troops had also been killed and injured in the fighting.
The UN's 17,000-strong Congo peacekeeping force - its biggest in the world - is trying to establish order across the country in the wake of a five-year war estimated to have killed nearly four million people, mainly through hunger and disease.
The war officially ended in 2003, but bands of gunmen still intimidate civilians in large areas, particularly in the east where mineral riches are believed to have fuelled the conflict that at one point drew in six foreign armies.
Reichen said UN forces would be heavily involved after March in election preparations and wanted to use the coming months to help pacify pockets in the east where rebels and militias attacked government troops and terrorised civilians.
UN helicopter gunships and armoured personnel carriers were supporting the operation in North Kivu against the rebel Ugandan Allied Democratic Forces/National Army for the Liberation of Uganda (ADF/NALU).
Reichen, who estimated their strength at around 1000, said: "The ADF is a tough nut to crack, they are hardened rebels."
Uganda and neighbouring Rwanda backed rebels in Congo's complex five-year war and nationals from both countries still operate in militia groups across Congo's east.