The U.N. human rights office is expressing concerns about "rapidly worsening" security and respect for human rights in Burundi after the shooting deaths of at least nine civilians in the capital.

Spokesman Rupert Colville says the Office of the High Commissioner for Human Rights estimates that 198 people have been killed in Burundi since April 26, including 63 in the last three weeks.

He said nine people including national TV cameraman Christophe Nkezabahizi, his family and Evariste Mbonihankuye, a staffer of the Geneva-based International Organization for Migration, were "reportedly summarily executed" by special police unit forces on Oct. 13 in the Ngagara neighborhood of Bujumbura, the capital.

Colville said an investigation was underway to determine the circumstances but added: "It appears to be an act of vengeance."