Fighting between Ethiopian government forces and rebellious northern leaders could spiral out of control and war crimes may have been committed, the United Nations said on Friday, as repercussions spread around the volatile Horn of Africa.

The 10-day conflict in Tigray region has killed hundreds, sent refugees flooding into Sudan, and raised fears it may draw in Eritrea or force Ethiopia to divert troops from an African force opposing al-Qaeda-linked fighters in Somalia.

It may also blemish the reputation of Prime Minister Abiy Ahmed, who won a Nobel Peace Prize for a 2018 peace pact with Eritrea and had won plaudits for opening Ethiopia’s economy and easing a repressive political system.

“There is a risk this situation will spiral totally out of control, leading to heavy casualties and destruction, as well as mass displacement within Ethiopia itself and across borders,” UN rights chief Michelle Bachelet said via a spokesman.

A massacre of civilians reported by Amnesty International, if confirmed as committed by a party to the conflict, would amount to war crimes, she added.

The U.S. State Department’s top diplomat for Africa on Friday denounced the killing of civilians in the conflict.

“We condemn the massacre of civilians in Mai-Kadra and strongly urge immediate steps to de-escalate and end conflict throughout the Tigray region,” Tibor Nagy tweeted.

“It is essential that peace be restored and civilians be protected.”

Prime Minister Abiy accuses the Tigray People’s Liberation Front (TPLF), which rules the mountainous region of more than five million people, of treason and terrorism.

Federal troops say the TPLF rose against them last week but that they have since survived a siege and recaptured the west of the region. With communications cut and media barred, there has been no independent confirmation of the state of the fighting.

The TPLF says Abiy’s government has systematically persecuted Tigrayans since he took office in April 2018 and terms the military operations an “invasion”.

Federal troops have been carrying out air raids and there has been fighting on the ground since Wednesday of last week.

Ethiopia denied a TPLF claim that federal jets had knocked out a power dam.

Civilians in the Sudanese border town of al-Fashqa, where more than 7,000 refugees have sought safety, gave first-hand accounts of the escalating conflict in Tigray to Reuters news agency on Friday.

Witnesses described bombing by government warplanes, shooting on the streets and killings by machete.

Many of them described seeing dead bodies strewn alongside the roads as they fled under cover of darkness, fearing they would be found and killed.

“I saw the bodies of people who had been slain thrown in the streets. Others who were injured were dragged with a rope tied to a rickshaw,” said Araqi Naqashi, 48.

“What happened is frightening and terrible, and the Tigrayans are being killed and chased down. Anything is looted, and our area was attacked with tanks.”