ADDIS ABABA/AL FASHQA, Sudan (Reuters) - The United Nations voiced concern on Friday that the conflict between Ethiopian government forces and insurgent northern leaders could spiral out of control and said war crimes may already have been committed.On the Sudanese border, refugees who had fled the combat zone in Tigray region told of buildings wrecked by government air raids, shootings in the street and killings by machete. The 10-day-old war has already killed hundreds, pushed thousands of civilians into Sudan, and raised fears it may draw in Eritrea or pressure Ethiopia’s commitment to an African force opposing al Qaeda-linked militants 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,” U.N. rights chief Michelle Bachelet said. A massacre of civilians reported by Amnesty International would amount to war crimes if confirmed it was commiited by one of the belligerent forces, she said. 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 persecuted Tigrayans and purged them from positions since he took office in April 2018, replacing a TPLF-led coalition in which he had served as a minister and head of a cyber security unit. It terms the offensive an “invasion”. Federal troops have been carrying out air strikes and there has been fighting on the ground since Wednesday of last week.