DAKAR, Senegal (AP) — Islamic militants and ethnic-based militias killed more than 450 civilians in central Mali last year, making it the deadliest year in the region since the country’s crisis began in 2012, Human Rights Watch said in a new report Monday.

Militants have even begun pulling men off of public transport based on their ethnicity and killing them, the group said, underscoring how Islamic extremists have inflamed tensions between communities that long lived in relative peace.

Islamic extremist groups have been recruiting men from the Peuhl ethnic group to their cause, while in turn the armed Dogon militias that have arisen are accused of supporting Mali’s military crackdown on jihadists.

Of the 456 civilian deaths documented by Human Rights Watch, 116 were directly blamed on the Islamic extremists. The remaining 340 killings were acts of communal violence carried out by ethnic-based militias, and the report said the true toll is unknown.

“Armed groups are killing, maiming, and terrorizing communities throughout central Mali with no apparent fear of being held to account,” said Corinne Dufka, West Africa director at Human Rights Watch. “The human toll in shattered lives is mounting as the deadly cycles of violence and revenge continue.”

Witnesses told investigators that in one instance last year jihadists had stopped two public transport vehicles that were bringing people back from a nearby market. Armed militants then dragged off 11 men who all belonged to the Dogon ethnic group at the checkpoint not far from Sevare.

Seven bodies were later found with bullets to the heads; the four others were never found, security forces told Human Rights Watch.

A French-led military operation ousted jihadists from power in northern Mali in 2013, though they dispersed and regrouped. By 2015, many had infiltrated much further south and began recruiting members of the Peuhl ethnic group.

While Malian courts convicted some 45 people last year in connection with some of the smaller attacks, “magistrates had yet to question powerful militia leaders implicated in the worst atrocities,” Human Rights Watch said.