United Nations peacekeepers in the Democratic Republic of Congo have killed more than 50 militiamen in a gun battle in the north-east, the UN says.
The mandate of the UN mission in DR Congo was strengthened last year
The fierce fighting came during a major offensive against an ethnic militia, accused of killing nine Bangladeshi UN soldiers in Ituri province last week.
A UN spokeswoman accused the militia of killing and raping civilians from rival groups, and said they must be stopped.
The UN force in DR Congo is one of the world's largest, at more than 13,000.
"While on operation we were fired upon, so we immediately responded," said Col Dominique Demange, a spokesman for UN forces in DR Congo.
He said the Pakistani UN troops had used helicopter gunships and armoured vehicles in the operation against the militia.
Those killed are believed to be from the ethnic Lendu Nationalist and Integrationist Front (FNI), whose leader has been arrested following the killing of the Bangladeshi peacekeepers.
The UN chief of staff in DR Congo, General Jean-Francois Collot d'Escury, vowed to dismantle all the militia camps in the area, saying his message to the gunmen was straightforward: the UN peacekeepers know how to fight.
However, one local Lendu leader told Reuters news agency that the UN mission in DR Congo (Monuc) was wreaking indiscriminate revenge.
"We say Monuc is looking for vengeance, and they are seeking it against the Lendus without even verifying exactly who it was who carried out the massacre of the Bangladeshis," said Larry Batsi Thewi.
Tuesday's clash took place near where the Bangladeshi troops were ambushed last week, outside Loga, 30 km (19 miles) north of Bunia, Ituri's provincial capital.
AFP news agency reports the militia were based on a plateau overlooking the town of Kafe, where more than 8,000 people have fled recent violence.
The FNI are accused of terrorising their ethnic Hema rivals in Ituri.
"This group continues to loot, kill and rape these people, making life miserable," said UN spokeswoman Eliane Nabaa.
"It's time to put an end to this militia."
Two UN soldiers were wounded in the latest clashes, said the UN office in Bunia.
On Monday, the Congolese government said three FNI commanders had been detained.
The three include the militia's leader, Floribert Ndjabu. The FNI denies killing the UN troops.
There are more than 13,000 peacekeepers in DR Congo, following a 2002 deal to end five years of civil war.
Thousands of people have fled ethnic violence in Ituri
But ethnic militias in Ituri have so far refused to disarm and have continued to fight for control over the region's rich natural resources.
As a result of the resumption of violence in the region, the UN humanitarian agency, Ocha, has stopped some of its activities, depriving more than 50,000 displaced civilians of humanitarian assistance.