Eyewitnesses told the BBC that they had seen what they believed to be Angolan and Zimbabwean soldiers dressed in the uniform of the Congolese army.
"We are seeing soldiers wearing the Congolese army uniform here in town but they are not speaking the same language as us," an anonymous resident in Goma told the British broadcaster. "They are unable to speak French, Swahili or Lingala - that is bizarre."
There have been persistent reports of Angolan soldiers on the ground in the DR Congo during the last few weeks of fighting, raising fears that the latest clashes could reignite the 1998-2003 war, which sucked in many other nations, including Angola, Rwanda and Zimbabwe.
More than 5 million people are estimated to have died as a result of the five-year conflict in the resource-rich nation, most of them from hunger and disease.
Angola denies it has provided troops, but southern African leaders have said they will send a peacekeeping force if necessary.
The United Nations peacekeeping mission in the DR Congo (MONUC) said it had not come across any Angolan soldiers during the fighting.
"Angola has a bilateral agreement with DR Congo and has said it will send troops if necessary ... but we have not seen any evidence of Angolan troops operating on the ground," Jean-Paul Dietrich, military spokesman for MONUC, told Deutsche Presse-Agentur dpa.
Aid agencies say that renewed fighting between Laurent Nkunda's National Congress for the Defence of the People (CNDP) and government forces has displaced at least 250,000 people since late August.
The fighting blew up into full-scale battles over two weeks ago when the CNDP began a major offensive, routing the Congolese army.
Fighting has continued despite Nkunda calling a ceasefire just as his troops were on the verge of taking Goma, the capital of North Kivu province.
Peacekeepers are defending Goma. But MONUC chief Alan Doss has said his troops are stretched to their limit by the conflict. MONUC has 17,000 troops across the entire sprawling central African nation.
Calls for another 3,000 UN troops to be deployed have so far not been answered with any firm commitments, but discussions are still in progress and it is expected the commitment will eventually come.
The DR Congo accuses Rwanda of backing Nkunda. Nkunda says he is fighting to protect Tutsis from Hutu militia who fled to DR Congo after the 1994 massacres in Rwanda, when 800,000 Tutsis and moderate Hutus were killed.
Rwanda denies this, but the Financial Times reported it had spoken to former rebels who said that some of Nkunda's men were Rwandan soldiers receiving their wages from Kigali, the Rwandan capital.
Nkunda has warned that unless the DR Congo government talks to him directly, his forces - believed to number between 4,000 and 6,000 -will march on the capital Kinshasa.
However, the rebel general was last Friday left out of talks in Nairobi, which were attended by UN Secretary General Ban Ki-moon, Congolese President Joseph Kabila and Rwandan President Paul Kagame.
Civilians have borne the brunt of the fighting. Many of those who fled were forced to flee without even basic supplies, such as blankets. They are now caught outside in the rainy season.
Non-combatants have also been targeted by both rebel and government forces.
MONUC said Tuesday that government soldiers looted from civilians in the Kanyabayonga area (175 kilometres north of Goma) and also raped women as they retreated from a rumoured CNDP advance.
Human Rights Watch also said Tuesday that at least 50 civilians were killed in the North Kivu town of Kiwanja, most of them by Nkunda's forces. dpa ml ncs
- Deutsche Presse Agentur
- Copyright (c) dpa Deutsche Presse-Agentur GmbH