Clashes with the M23 continued on Tuesday about 30 kilometers west of Goma, a city of over one million people, according to a security official who declined to be named.
M23 fighters also remained in their positions several dozen kilometers north of Goma.
The rebels are close to encircling the city, which is sandwiched between Lake Kivu and the Rwandan border, with three out of four roads leading out of it cut off.
On Monday, the Tutsi-led group seized the town of Mweso, about 100 kilometers west of the provincial capital Goma.
Local civil society leader Alphonse Habimana told AFP on Tuesday that the M23 was in control of the town of 30,000 people.
Heritier Ndangendange, spokesman for the APCLS - one of the militias fighting the M23 - confirmed that rebels had captured Mweso.
On February 17, East African leaders urged all non-state armed groups to withdraw from territory they occupy in eastern Congo by March 30.
The withdrawal was intended to take place in three stages, with the initial phase to begin on February 28.
The M23 re-emerged from dormancy in November 2021, accusing the DRC of ignoring a promise to integrate its fighters into the army.
It subsequently won a string of victories over state forces, seizing swathes of territory in North Kivu province and displacing hundreds of thousands of people.