"They did not use firearms, but knives and machetes, and they killed three Indians and critically injured another three."
Egide Karafifi, the head city official in Kirumba, told the AFP news agency that the attackers were wearing civilian clothes, had raphia palm coverings on their heads and were singing Mai-Mai songs.
The Mai-Mai are just one of a number of armed groups fighting each other and the army in the east of the country.
They were integrated in the Congolese army but control their own territory in South Kivu province and have previously attempted to overturn the military command in the area.
"It's a very sad loss but I can assure you that we will pursue our efforts against the threats posed by the various armed groups, including the group which launched the attack this morning"
head of the UN mission
in DR Congo
No group immediately claimed responsibility for the killings.
Roger Meece, the head of the UN mission in DR Congo, said the deaths were "a very sad loss," but added that his forces would continue their efforts to beat the threat of armed groups operating in the region.
"I can only reiterate the shock I felt, the sadness for the loss of our soldiers," Meece said at his weekly news conference in Kinshasa.
"It's a very sad loss but I can assure you that we will pursue our efforts against the threats posed by the various armed groups, including the group which launched the attack this morning."
Nearly 4,000 Indian army soldiers are part of the UN Congo peacekeeping mission, which has about 20,000 people from various countries.
An Indian peacekeeper was shot and killed in North Kivu in May this year, and another was killed in a gun battle in the province in 2005.
Ban Ki-moon, the UN secretary general, called for an investigation into the latest killings.
"The secretary-general condemns the assault and calls on the government of the Democratic Republic of the Congo to launch an immediate investigation into this incident and ensure that the perpetrators are swiftly identified and brought to justice," a UN statement said.
Urged to leave
Repeated attacks have called into question the ability of the UN force to protect civilians. The mission, earlier known by its French acronym Monuc, has lost more than 100 peacekeepers since 1999.
It has been present in DR Congo since late 1999 and its mandate runs until June 30 next year.
DR Congo's president has said that he wants all the peacekeepers out before September 2011 and the UN started a nominal withdrawal last month.
However, John Holmes, the UN humanitarin chief, and non-governmental groups have warned that violence may spiral out of control if the peacekeepers all leave.
Rebels ousted longtime dictator Mobutu Sese Seko in 1997, then turned on each other in back-to-back civil wars that became an international scramble for the country's minerals and drew in soldiers from more than a half-dozen African nations.
The $1.35 billion-a-year UN mission helped hold DR Congo's first democratic elections in 40 years in 2006, although results were disputed and critics said the process favored the incumbent, Joseph Kabila.