About 40 people have died in eastern Democratic Republic of Congo in a clash between Ugandan rebels and Congolese forces backed by United Nations troops.
UN and Congolese troops fought together against the militia
The fighting took place when the Allied Democratic Forces rebel group launched a counter-attack against the Congolese and UN soldiers in North Kivu province.
An Indian UN peacekeeper and three Congolese troops were among the dead.
The UN says its operation in the area seeks to bring security to people harassed by hundreds of militiamen.
The operation in the region, known as North Night Final, involves 3,500 Congolese troops, supported by 600 UN peacekeepers using helicopter gunships.
The UN and Congolese troops were attacked in the early hours of Sunday after the UN tried to search the area, 30km south of the town of Beni.
The death of the Indian peacekeeper brings to 60 the total number of UN peacekeepers killed since the beginning of the UN deployment in DR Congo six years ago.
Since last week, more than 500 UN peacekeepers from Bangladesh, Nepal and Morocco, and about 3,000 Congolese soldiers, have also been conducting other large operations in the nearby district of Ituri, aiming at restoring peace.
They are trying to recapture some areas that have been under the control of militiamen there.
On Saturday, the UN announced the Congolese army had recaptured the former rebel stronghold of Nioka, 80km north of Bunia.
Militiamen remain active despite the presence of 16,000 UN peacekeepers countrywide: their largest military operation in the world.
Rebels attacked electoral officials in last week's referendum on a new constitution.
The BBC's Arnauld Zajtman in Kinshasa says it is feared the militia groups will disrupt the first round of general elections, due in March.