"The rebels are here," a resident of Tongo, a town in wildlife haven Virunga National Park, which lies on the road leading to Masisi territory, said on Thursday.
An official in the local administration, who requested anonymity, also told AFP late Wednesday that M23 fighters had entered his office.
M23 fighters and Congolese troops were clashing this week in Kibumba, which is just 20 kilometers north of Goma.
Thousands of people packed their belongings and headed towards Goma on Tuesday, amid rumours of a rebel advance, after troops were seen fleeing.
The following day, a military tribunal in Goma sentenced three to death for "cowardice" and having "fled before the enemy," among other charges, a court official said.
In practice, the death penalty in the DRC is commuted to life imprisonment.
On Thursday, the DRC deployed two warplanes against advancing M23 militants, targeting positions in Kibumba at noon, according to a resident who spoke to AFP via telephone from the region's main city Goma.
A security official, who declined to be named, said Thursday the M23 now controlled the settlement.
The DRC's army has yet to communicate officially about the rebel advance.
But an unpublished report for the United Nations seen by AFP aid the M23 plans to capture Goma in order to extract political concessions from the government in Kinshasa.
In recent weeks, fighters have been edging closer towards Goma, an important commercial hub of one million people on the border with Rwanda.
But local residents and administrative officials told AFP that the armed group had also begun a push westwards into Masisi territory.
Meanwhile, on Wednesday, the head of the newly created East African Community (EAC) military force in eastern DR Congo, Jeff Nyagah, said that rebels that must pursue political negotiations and disarm.
"Those who fail or refuse to voluntarily disarm, then we'll go for them," the Kenyan general warned.
Nyagah also vowed that the EAC force would protect Goma.
A resurgent group mostly drawn from DRC Tutsis, the M23 has swept across North Kivu province, triggering a humanitarian crisis and a showdown between the DRC and Rwanda, which Kinshasa accuses of supporting the rebels - an assertion Rwanda strongly denies.
