The UN on Thursday sent tanks into the eastern Congolese town of Goma to fend off a possible attack by M23 rebels.
AFP reported a dozen tanks had moved into the capital of North-Kivu province in the Democratic Republic of Congo.
It comes as the government signed an agreement with Rwanda, Burundi and Uganda to “eradicate armed groups” in the east of the country.
DR Congo has been wracked by inter-ethnic conflict for much of the past two decades.
Militias also fight with the state for access to lucrative mining resources.
The M23, or March 23 Movement, is an ethnic Tutsi rebel group that took up arms in April.
It takes its name from a failed peace deal signed three years ago.
Such groups have long clashed with the government and Hutu rebels, some of whom participated in the 1994 Rwandan genocide.