The U.N. human rights chief is warning of worrying new trends in Burundi such as gang-rapes of women by security forces, torture and signs of ethnic repression in nine months of simmering violence and repression.

President Pierre Nkurunziza's decision to seek a third term last year has left Burundi on the brink of civil war. The office of U.N. rights chief Zeid Raad al-Hussein's said Friday that 432 people have been killed in violence since April 26.

Zeid said his office was analyzing satellite images to shed light on allegations about the reported discovery of nine mass graves. His office also cited growing signs that Tutsis were being targeted in the Hutu-majority country neighboring Rwanda.

"All the alarm signals, including the increasing ethnic dimension of the crisis, are flashing red."