RwandAir (WB, Kigali) has cancelled all its flights to Kinshasa N'Djili, Lubumbashi, and Goma with immediate effect following the decision by the Democratic Republic of the Congo (DRC) to suspend all its incoming flights amid growing political tension between the neighbouring states.

The cancellation on May 28 followed a day after the DRC summoned Rwanda's ambassador and suspended RwandAir flights in response to what it claimed was Kigali's support for M23 rebels carrying out a military offensive in the eastern province of North Kivu, which borders Rwanda.

Rwanda has denied supporting the rebels. Last week, government spokeswoman Yolande Makolo said the country had "no intention of being drawn into an internal matter of the DRC".

RwandAir, in a statement, said it considered "the safety and security of its customers and crew as [its] number one priority". It would waive change of reservation fees and offer re-issues or refunds for affected passengers.

Reuters reported that the DRC's army had been engaged in heavy fighting against the M23 rebel group since the weekend. M23 advanced as close as 20 km to Goma and briefly captured the DRC army's largest base in the area.

M23, formerly the March 23 Movement and also known as the Congolese Revolutionary Army, claims to defend Tutsi interests against ethnic Hutu militias like the Democratic Forces for the Liberation of Rwanda (FDLR), which for its part was founded by Hutus who fled Rwanda after participating in the 1994 genocide. M23 refers to a March 23, 2009, accord that ended a previous Tutsi-led revolt in eastern Congo.

Late on Friday, DRC government spokesman Patrick Muyaya announced the suspension of RwandAir flights and the summoning of the Rwandan ambassador following a meeting of the DRC National Defence Council.

He said the government had designated M23 a terrorist group and would exclude it from negotiations held in Kenya with militia groups active in eastern Congo.

"A warning was made to the Rwandans, whose attitude is likely to disrupt the peace process ... where all the armed groups, except for the M23, are committed to the path to peace," Muyaya said.

Kenya is trying to broker dialogue between the warring parties, having hosted talks in Nairobi in April between the DRC and M23.