Forces attacked eight "enemy camps" in eastern Congo last Friday with air and artillery strikes, according to the military statement.
The operation targeted the Allied Democratic Forces, which has battled governments in East Africa since the 1990s and has ties to several international jihadi groups. The organization has previously been sanctioned by the United States and the United Nations for terrorist activities.
The slain peacekeepers hailed from Tanzania. Along with those victims, five Congolese soldiers were killed and 53 others were injured, according to the UN peacekeeping mission in the Democratic Republic of Congo. The attack took place in North Kivu, an eastern province that borders Rwanda and Uganda.
"The ADF recent attack on the UN Peacekeepers of MONUSCO from the sister-country of Tanzania is an indictment to its activities not only for Uganda and DRC but also the international community," Uganda's Defense Spokesman Richard Karemire said in the statement. "The population in the affected areas, the region, and international partners shall be mobilized to stop terrorist activities once and for all."
The strike, described as the worst against UN "blue helmets" in recent history, prompted world and regional condemnation and calls for vigilance. The UN Security Council condemned the attack.
"These deliberate attacks against United Nations peacekeepers are unacceptable and constitute a war crime," UN Secretary-General Antonio Guterres said.
The US Department of Treasury
denounced the ADF "for targeting children in situations of armed conflict, including through killing, rape, abduction and forced displacement." The United Nations
also admonished the group, citing "serious violations of international law and the recruitment of child soldiers."
"The ADF, with an estimated 1,200 to 1,500 armed fighters, launched a series of attacks in 2013 against civilians in the DRC, forcing thousands of people to flee into Uganda and abducting or killing those that attempted to return," the Treasury department said in a statement.
"The ADF was also responsible for brutal attacks on women and children in several villages, including acts of beheading, mutilation, and rape," the statement said. "In recent years, the ADF has boosted its numbers through kidnapping as well as recruiting children, allegedly as young as 10 years old, to serve as child soldiers against the Ugandan government."
The Ugandan military said Congolese forces are pursuing the survivors of the assault who "are roaming in different areas of North Kivu." Uganda has established operations at its borders "to deter any of the terrorists from sneaking into our territory."
"Should they attempt to attack our border villages, (Uganda People's Defense Forces) shall not hesitate to pursue them to wherever they will have come from," the Uganda military spokesperson said.