Rwanda on Tuesday accused Uganda of supporting rebel groups opposed to President Paul Kagame’s government, amid a resurgence of hostility between the African neighbours.

Relations between the two nations soured last week after Rwanda blocked Ugandan cargo trucks from entering its territory at the busiest crossing point, Katuna, and barred its nationals from crossing into Uganda.

Officials in Kigali say they have directed trucks to another border point 100 km (60 miles) away, but hundreds of them are still stuck at the frontier.

Rwandan Foreign Minister Richard Sezibera accused Uganda of offering succour to two foreign-based Rwanda rebel groups – Rwanda National Congress (RNC) and Democratic Forces for the Liberation of Rwanda (FDLR).

“RNC and FDLR work from Uganda with support of some authorities there. This is another serious case and we have raised it with them,” he told a news conference in Kigali.

The RNC is a rebel group led by some of Rwanda’s most prominent dissidents including South Africa-based Kayumba Nyamwasa. Its founders say it is a political party.

The FDLR is a rebel group composed in part of former Rwandan soldiers and Hutu militias who fled into Democratic Republic of Congo after massacring around 800,000 Tutsis and moderate Hutus during Rwanda’s 1994 genocide.