Madnodje Mounoubai, a spokesman for the U.N. peacekeeping mission in DRC, said Tanzanian soldiers deployed to Goma, the capital of North Kivu province.
"From the evidence we have, about 100 elements are already in place," he told U.N.-backed Radio Okapi. "These are officers, members of staff, so those responsible for planning ... have arrived."
The U.N. Security Council in March backed a special unit within the peacekeeping mission that would have combat duties.
Rights group said the intervention brigade would raise the risk of reprisal attacks, however.
The rebel March 23 Movement seized control of parts of eastern DRC last year. Former M23 leader Bosco Ntaganda surrendered to the International Criminal Court, where he's the subject of two arrest warrants for war crimes committed in DRC.
The U.S. State Department said it was concerned about the security situation in the DRC, describing the security situation in the east of the country as "tense and fragile."