At least 14 UN peacekeepers were killed and 53 wounded in the Democratic Republic of Congo.
The UN mission, Monusco, said security forces attacked the suspected rebel allied rebel on Thursday in Semulik province, North Kivu.
Five more soldiers with the DR Congo (FARDC) were killed.
Congo has experienced many years of instability with competing groups struggling for regional control.
On Friday, Jean-Pierre Lacroix, general secretary of peacekeeping, said the reinforcements had been sent and medical transfers were under way.
Monuscu leader Maman Sidikou said in his statement: “We strongly condemn this deadly attack on UN peacekeepers and the FARDC guardians.
“Monusco will take all measures to ensure that the factors are taken into account and brought to justice.”
Citizens of peacekeepers are not mentioned, although UN officials say they are from Tanzania.
Several armed forces are struggling in mineral resources in northern Kivu.
Democratic Republic of Congo
Earlier this week, aid organizations said the conflict forced 1.7 million people in the Democratic Republic of Congo to flee their home this year.
President of the Democratic Republic of Congo, Norwegian Refugee Council, Ulrika Blom described the situation as a “mega crisis”.
“Population scales fled is offline, Syria, Yemen and Iraq,” he said.