Congolese army and UN peacekeeping troops carried out a "cordon and search" operation on Monday in the militia strongholds of the embattled northeastern district of Ituri, killing scores of militiamen.
Eliane Nabaa, a spokeswoman of the UN Mission in the Democratic Republic Congo (DRC), known as MONUC, said the exact number of the militiamen killed could not be established immediately, but news reports put the deaths at between 15 and 20.
The operation, during which several militia camps were destroyed, focused on Katoto and Lingo areas, 25 km northeast of Bunia, the main town in Ituri.
Nabaa said these areas were under the control of the Union des patriotes congolais (UPC) militia group. The dead militiamen were in the Lingo area.
"More than 1,000 UN forces from Bangladesh, Pakistan and Morocco have been mobilised with the back-up of armoured vehicles and combat helicopters to dismantle five militia camps at Lopa, Lingo and Katoto," she said.
She added that another 18 militiamen from Lingo had disarmed at a transit centre, and that disarmament would continue in the area for a "few" more days.
Armed militia groups in Ituri have been accused of routinely committing atrocities and other human rights abuses that have led to the displacement of hundreds of thousands of civilians.
"We shall continue the effort to isolate these militias and encourage the people to come back to their villages," Nabaa said.
The Katoto-Lingo operation was the third by MONUC to disarm the militias, following the expiry of its 1 April deadline for the fighters to disarm voluntarily.
Fighting in the district has caused the death of at least 60,000 and the displacement of 500,000 others since 1998.
MONUC said of the 13,000 militiamen estimated to be in the district; only 10,644 had disarmed by Tuesday. They are in seven transit centres across the district. Of those disarmed, only 1,286 were from UPC.
UN troops deployed across the country, as well as troops of the newly integrated Congolese army brigades, are seeking to restore security in the country riven by years of war.
The transitional government of national unity, led by Joseph Kabila, is due to end with general elections in June.