The Democratic Republic of Congo has suspended RwandAir flights and summoned Rwanda's ambassador in response to what it says is Kigali's support for the M23 rebel group's offensive in eastern Congo.
Rwanda denies supporting the rebels, who advanced as close as 20 km this week to eastern Congo's main city of Goma and briefly captured the army's largest base in the area.
Congo and UN investigators had also accused Kigali of supporting the M23 during a 2012-2013 insurrection that briefly captured Goma. Rwanda denied those charges.
Congo's government spokesman Patrick Muyaya announced the suspension of flights from Rwanda's national carrier and the summoning of the ambassador late Friday night following a meeting of the national defence council chaired by Congolese President Felix Tshisekedi.
He also said Congolese authorities had designated the M23 a terrorist group and would exclude it from on-and-off negotiations being held in Kenya's capital Nairobi between Congo's government and militia groups active in the east.
"A warning was made to the Rwandans, whose attitude is likely to disrupt the peace process that is nearing its end with the discussions in Nairobi, where all the armed groups, except for the M23, are committed to the path to peace," Muyaya said.
RwandAir responded Saturday by cancelling "with immediate effect" all flights to Kinshasha, Lubumbashi and Goma, the airline said in a statement.
Kinshasa also accuses Kigali of scuppering a peace process being mediated by Kenyan President Uhuru Kenyatta, who holds the rotating presidency of the East African Community group.
Primarily a Congolese Tutsi group, M23 is one of more than 120 armed groups that roam eastern DR Congo, many of which are a legacy of regional wars more than two decades ago.
It briefly captured the provincial capital Goma in North Kivu in late 2012, before the army quelled the rebellion the following year.
M23 resumed fighting this year, accusing the Congolese government of failing to respect a 2009 agreement under which its fighters were to be incorporated into the army.
Recent clashes between the military and M23 rebels in eastern DRC have displaced 72,000 people, the United Nations said on Friday, compounding Africa's worst displacement crisis.