UN Secretary-General Ban Ki-moon on Thursday called for a “rigorous and prompt” investigation after nine civilians and two police officers were killed in Burundi on Oct. 13, said a statement of the secretary-general’s spokesperson.

Ban condemned the killing of nine civilians and two police officers in the capital Bujumbura, amid exchanges of heavy of gunfire in several neighbourhoods of the city, it said.

“The civilians, including a staff member of the International Organization for Migration, Mr. Evariste Mbonihankuye, were reportedly shot at close range,” it said.

According to AFP, a Burundian journalist, Christophe Nkezabahizi, his wife and two teenage children were among the victims and they were killed in their home.

Ban urged “Burundian authorities to undertake a rigorous and prompt investigation into the circumstances and motives behind these despicable crimes in order to ensure that their perpetrators are brought to justice,” it said.

Waves of violence persisted after the re-election of President Pierre Nkurunziza, whose announcement to contest for a third term stirred up protests.

The opposition and civil society groups opposed his candidature, arguing that the Arusha Agreement stipulated that a president serves for only two terms.