The attack, one of the deadliest on U.N. forces in the country, occurred near the town of Kafe, 20 miles northwest of Bunia, Ituri's capital.
"These blue helmets were out there protecting people, and they got ambushed while doing it," U.N. spokesman Mamadou Bah told the Associated Press.
The nine soldiers, all Bangladeshis, were among 4,800 soldiers from four nations overseeing a fragile peace in Congo -- formerly Zaire -- a country still recouping from a five-year civil war.
Though U.N. Undersecretary-General for Peacekeeping Jean-Marie Guehenno could not confirm the deaths, he did say that nine Bangladeshi troops had gone missing and were believed to be dead.
An additional force of 90 U.N. troops had been sent to the scene along with Mi25 attack helicopters, a source told Reuters, though heavy rain in the district had made a search and rescue operation tenuous.
Two of the peacekeepers died on the spot while seven others may have been taken into the bush and executed, the source said.
The soldiers were patrolling a region near the main city of Bunia, controlled by a predominantly ethnic Lendu militia known as FNI.
"Lendus are not people that take hostages, they just kill," the source said.
On Friday, MONUC, the United Nations Mission in the Democratic Republic of Congo, released a statement calling the killing of its soldiers a "premeditated attack" and resolving to remain in the region, according to Reuters.
"This attack can only strengthen MONUC's resolve to continue its actions aiming at neutralising the armed groups and protect the population," the statement said.
U.N. Secretary-General Kofi Annan also condemned the attacks and called on the Democratic Republic of Congo to aid in identifying the attackers.
Some 16,000 U.N. troops -- the largest U.N. force in the world -- are in Congo charged with maintaining the measures of a peace deal signed in 2003 by government forces and rebel leaders.
The peace deal and the subsequent formation of a transitional government ended what many believe to be the deadliest civil war in Africa, one that drew in five neighboring nations and, at its end, left an estimated 3 million people dead.
Fought over Congo's rich mineral resources, including diamonds, coffee and in some areas crude oil, the war drew international attention, including a visit to the region from President Clinton in 1998 and efforts to mediate peace from South African President Nelson Mandela.
In 2003, current Congolese President Joseph Kabila took office following the murder of his father, president and former rebel chief Laurent Kabila. The younger Kabila, who was only 30 when he came to power, has since made attempts to maintain peace and usher Democracy into the war-torn country.
General elections, the first since Zaire's independence from Belgium in 1960, are scheduled for June 2005, the BBC reported.
Ituri, one of the country's most lawless regions where the Kinshasa-based government has little to no control, has been the scene of increased violence in recent years. Ethnic militias have killed an estimated 50,000 civilians since 1999, according to Reuters, leading the U.N. to station about a third of its Congolese force in the area.