UN peacekeepers killed at least 50 militiamen in a gunfight in northeastern Congo Tuesday, five days after nine Bangladeshi UN troops were killed there, the United Nations said yesterday.

Militia fighters opened fire on Pakistani peacekeepers hunting those responsible for attacks on civilians, wounding two of the UN soldiers and triggering a fierce battle involving helicopter gunships, UN officials said.

The clash in the mineral-rich but lawless Ituri province was one of the biggest involving UN troops deployed in the Democratic Republic of Congo.

"I can confirm 50 Congolese militiamen were killed," said Rachel

Eklou, a U.N. spokeswoman in Bunia, Ituri's main city. A senior source in the peacekeeping operation said the number of dead could be between 50 and 60.

Tuesday's clash happened at Loga, close to the area where the Bangladeshi peacekeepers were killed in the worst single loss suffered by the United Nations' peace mission since it began in the former Zaire in 1999.

The UN representative in Congo, William Lacy Swing, told the news agency there could be more such actions.

"We had a major operation at Loga yesterday that was conducted both by ground and air assets," he said. "I think you will see us moving in this direction more and more."

A UN military source said the dead fighters were members of the Nationalist and Integrationist Front (FNI) militia.

The FNI is an ethnic Lendu-dominated militia which has been battling rival Hema factions in a conflict that has killed more than 50,000 people in northeastern Congo since 1999.

Under intense pressure from the United Nations and foreign states to track down the peacekeepers' killers, Congo's government said yesterday it had arrested an FNI leader and was investigating three Ituri warlords-turned-generals.

Another senior FNI commander surrendered to UN forces in Ituri, a UN spokeswoman said.

Miltiamen roam vast swathes of the east of Africa's third-biggest country, raping and pillaging. Their conflict is rooted in land and commercial rivalries in a region rich in gold, timber and diamonds.

Congo's Defense Minister Adolphe Onusumba told the news agency in Bunia that he supported the action of the UN troops, known by their French acronym MONUC.

"I was not informed about any operation that was conducted by MONUC in the area ... but anything that is done to dismantle these militias is in the interest of the Congolese," he said.

Congo's fragile government is struggling to impose its authority on the eastern warlords and said on Monday a further 3,000 soldiers would be sent to support a brigade in Bunia.

The fighting in the east has cast a shadow over Congo's efforts to draw a line under a wider five-year war that officially ended in 2003 and which killed nearly 4 million people, mostly from hunger and disease.

Elections are due to be held in June, but instability in the east as well as logistical problems have raised questions about whether the polls can be held on time.