Patrick Karegeya, Rwanda's former foreign intelligence chief turned opponent, was found dead in a hotel room in Johannesburg on 31 December last year. The home of Kayumba Nyamwasa, Rwanda's former army chief of staff who also lives in exile, was targeted on 4 March 2013.
South Africa expelled four Rwandan and a Burundian diplomats. All were accused of criminal activities incompatible with their diplomatic status. They were allegedly involved in the killing of Karegeya and attempts on the life of Nyamwasa.
Pretoria declared it had evidence of the diplomats' involvement, but gave no further details. Rwanda expelled six South African diplomats in retaliation.
It claims Pretoria gave shelter to terrorists and accused the two opponents of being behind grenade attacks that took place in Rwanda.
The USA has condemned the killing of Karegeya and the attack on Nyamwasa's home. Washington said that it found troubling the series of killings of Rwandan exiles seemingly for political reasons and that it was concerned by statements made recently by Rwanda's president.
On 12 January Paul Kagame said that "treason brings consequences".