South Africa has expelled three Rwandan diplomats it says were linked to a raid by gunmen this week on the Johannesburg home of a dissident exiled Rwandan general.
A diplomatic source told Reuters on Friday that Rwanda had retaliated by ordering out six South African diplomats.
Late on Monday, a group of armed men broke into the South African home of former Rwandan army chief Faustin Kayumba Nyamwasa, an exiled critic of the Rwandan president Paul Kagame, who survived a previous assassination attempt in Johannesburg in 2010.
The source said South African security services had tracked the perpetrators of the attack. "It was very clear that they were intelligence personnel attached to the Rwandan embassy," the source said.
This resulted in the three diplomats from the Rwandan mission in Pretoria being ordered out of the country in 48 hours. Kigali's tit-for-tat expulsions occurred on Friday, the source added.
South African police have also been investigating the New Year's Eve murder in a posh Johannesburg hotel of another exiled opponent of Kagame, former Rwandan spy chief Patrick Karegeya.
Kagame and senior Rwandan officials have denied any involvement in the attacks on exiled opponents, but have called them traitors who should not expect forgiveness or pity.