Evidence is increasing that foreign forces are being drawn into the conflict in the east of the Democratic Republic of Congo.
Eyewitnesses told the BBC Angolan and Zimbabwean troops were on the ground.
Meanwhile, journalists report that some of Laurent Nkunda's rebel fighters are in the pay of the Rwandan army.
This has renewed fears that the fighting will see a re-run of the five-year Congolese war, which involved nine nations, before it ended in 2003.
Some 250,000 people have fled the most recent violence which flared in August between government forces and rebels demanding protection from Rwandan Hutu rebels who fled to DR Congo after Rwanda's 1994 genocide.
Gen Nkunda's rebels have told AFP news agency that they have advanced to the outskirts of Kanyabayonga, 100km (60 miles) north of the regional capital, Goma, where government forces were accused of looting and raping civilians earlier in the week.
The UN has accused both sides of war crimes during the latest upsurge in violence.
Despite a peace deal, the presence of the world's largest peace force and UN-backed elections, the resource-rich east of the country remains unstable.
"We are seeing soldiers wearing Congolese army uniform here in town but they are not speaking the same language like us. They are unable to speak French, Swahili or Lingala - that is bizarre," he told the BBC's Network Africa programme.
Experts say this evidence is not conclusive, since some Congolese troops, including a group known as the Katangan Tigers, fought in Angola during their civil war, and frequently converse in Portuguese.
Angola denies sending troops into DR Congo, although says it would support the government if called on to do so by the regional grouping, the Southern African Development Community.
During the last war, Congolese government forces supported by troops from Angola, Zimbabwe and Namibia, were fighting rebels backed by Uganda, Rwanda and Burundi.
Forces from Chad and Central African Republic were also involved in that conflict.
The war, which erupted in August 1998, was the largest on the continent in recent times.