Armed fighters from the M23 group, which has taken control of eastern DR Congo's key major town of Goma, on Saturday set about expelling thousands of people they say are illegals from Rwanda, AFP witnessed.

On Monday, the group's military spokesman, Willy Ngoma, had presented to the media 181 men whom they referred to as "Rwandan subjects" illegally in the country at Goma's main sports stadium.

All of the men shown had ID papers from the DRC, which the M23 asserted were bogus. An AFP reporter said the armed group had summarily burned the documents on the stadium pitch.

Several hundred women and children, relatives of those detained, joined them at the stadium aboard trucks chartered by the M23.

One of the men arrested, who gave his name only as Eric, had told AFP on Monday that he was from the town of Karenga, located in North Kivu, which is considered a stronghold of the Democratic Forces for the Liberation of Rwanda (FDLR).

The FDLR is an armed group founded by former Rwandan Hutu leaders of the 1994 Tutsi genocide.

Early Saturday, 360 people were loaded onto buses from Goma, Eujin Byun, a spokesperson for the United Nations High Commissioner for Refugees (UNHCR), told AFP.

The UNHCR stressed that "returns of refugees to their countries of origin must be safe, voluntary, and carried out with dignity, per international law".

An AFP correspondent reported that the convoy crossed the border to Rubavu, in western Rwanda.

"We will do everything to reintegrate them into society, so that they have the same responsibilities and the same rights as other Rwandans," Prosper Mulindwa, mayor of Rubavu district, told reporters.

The M23 and Kigali accuse Kinshasa of supporting the FDLR and have justified their offensive in eastern DRC by a need to neutralise that group.

The majority of the families expelled by the M23 are from Karenga, and had been prevented from returning there after the M23 took over Goma, according to security and humanitarian sources.

The families were living in a reception centre for displaced persons in Sake, some 20 kilometres (13 miles) from Goma, the sources said.

In March, 20 suspected FDLR fighters, dressed in Congolese Armed Forces uniforms, were handed over to Rwandan authorities by the M23.

Kinshasa denounced the incident as a "crude fabrication" intended to discredit its army.