A Burundian member of the East African Legislative Assembly was shot dead on Wednesday in what Rwanda's foreign minister called an assassination in a country in violent political turmoil.
Hafsa Mossi, a former minister in President Pierre Nkurunziza's government, was "shot by criminals" in the capital Bujumbura, the president's media adviser Willy Nyamitwe tweeted.
More than 450 people have been killed since Nkurunziza pursued and won a third term last year, a move that his opponents say violated the constitution and a peace deal that ended a civil war in 2005.
Government officials and members of the opposition have been among those killed in tit-for-tat violence by rival sides.
Louise Mushikiwabo, the Rwandan minister of foreign affairs, tweeted that she was mourning the loss of Mossi who had been "assassinated".
The upsurge in violence in Burundi has caused alarm in a region where memories of Rwanda's 1994 genocide remain raw. Like Rwanda, Burundi has an ethnic Hutu majority and a Tutsi minority.
So far the violence has largely followed political rather than ethnic lines. But diplomats fear ethnic wounds could re-open the longer violence continues.
Mossi had represented Burundi at the regional parliament since 2012 and her term was set to run until next year, according to the assembly's website.